Blank page for wizard when "similar topics" enabled

Environment

Discourse Version: 2.7.7

Plugin Commit: 0.8.1 version

Steps to Reproduce

Go to manage wizards
Enable “similar topics” for wizard text field
Make sure to add a category (without a category specified, it works)
when opening the wizard, blank page appear

Example

Logs

activemodel (6.1.3.2) lib/active_model/attribute_methods.rb:469:in `method_missing'
plugins/discourse-custom-wizard/serializers/custom_wizard/wizard_serializer.rb:61:in `block in categories'
plugins/discourse-custom-wizard/serializers/custom_wizard/wizard_serializer.rb:61:in `map'
plugins/discourse-custom-wizard/serializers/custom_wizard/wizard_serializer.rb:61:in `categories'
(eval):12:in `_fast_attributes'
active_model_serializers (0.8.4) lib/active_model/serializer.rb:468:in `rescue in attributes'
active_model_serializers (0.8.4) lib/active_model/serializer.rb:455:in `attributes'
active_model_serializers (0.8.4) lib/active_model/serializer.rb:480:in `_serializable_hash'
active_model_serializers (0.8.4) lib/active_model/serializer.rb:359:in `serializable_hash'
active_model_serializers (0.8.4) lib/active_model/serializer.rb:347:in `as_json'
app/controllers/application_controller.rb:495:in `serialize_data'
app/controllers/application_controller.rb:504:in `render_serialized'
plugins/discourse-custom-wizard/controllers/custom_wizard/wizard.rb:45:in `block (2 levels) in index'
actionpack (6.1.3.2) lib/action_controller/metal/mime_responds.rb:214:in `respond_to'
plugins/discourse-custom-wizard/controllers/custom_wizard/wizard.rb:36:in `index'
actionpack (6.1.3.2) lib/action_controller/metal/basic_implicit_render.rb:6:in `send_action'
actionpack (6.1.3.2) lib/abstract_controller/base.rb:228:in `process_action'
actionpack (6.1.3.2) lib/action_controller/metal/rendering.rb:30:in `process_action'
actionpack (6.1.3.2) lib/abstract_controller/callbacks.rb:42:in `block in process_action'
activesupport (6.1.3.2) lib/active_support/callbacks.rb:117:in `block in run_callbacks'
app/controllers/application_controller.rb:395:in `block in with_resolved_locale'
i18n (1.8.10) lib/i18n.rb:314:in `with_locale'
app/controllers/application_controller.rb:395:in `with_resolved_locale'
activesupport (6.1.3.2) lib/active_support/callbacks.rb:126:in `block in run_callbacks'
activesupport (6.1.3.2) lib/active_support/callbacks.rb:137:in `run_callbacks'
actionpack (6.1.3.2) lib/abstract_controller/callbacks.rb:41:in `process_action'
actionpack (6.1.3.2) lib/action_controller/metal/rescue.rb:22:in `process_action'
actionpack (6.1.3.2) lib/action_controller/metal/instrumentation.rb:34:in `block in process_action'
activesupport (6.1.3.2) lib/active_support/notifications.rb:203:in `block in instrument'
activesupport (6.1.3.2) lib/active_support/notifications/instrumenter.rb:24:in `instrument'
activesupport (6.1.3.2) lib/active_support/notifications.rb:203:in `instrument'
actionpack (6.1.3.2) lib/action_controller/metal/instrumentation.rb:33:in `process_action'
actionpack (6.1.3.2) lib/action_controller/metal/params_wrapper.rb:249:in `process_action'
activerecord (6.1.3.2) lib/active_record/railties/controller_runtime.rb:27:in `process_action'
actionpack (6.1.3.2) lib/abstract_controller/base.rb:165:in `process'
actionview (6.1.3.2) lib/action_view/rendering.rb:39:in `process'
rack-mini-profiler (2.3.2) lib/mini_profiler/profiling_methods.rb:85:in `block in profile_method'
actionpack (6.1.3.2) lib/action_controller/metal.rb:190:in `dispatch'
actionpack (6.1.3.2) lib/action_controller/metal.rb:254:in `dispatch'
actionpack (6.1.3.2) lib/action_dispatch/routing/route_set.rb:50:in `dispatch'
actionpack (6.1.3.2) lib/action_dispatch/routing/route_set.rb:33:in `serve'
actionpack (6.1.3.2) lib/action_dispatch/journey/router.rb:50:in `block in serve'
actionpack (6.1.3.2) lib/action_dispatch/journey/router.rb:32:in `each'
actionpack (6.1.3.2) lib/action_dispatch/journey/router.rb:32:in `serve'
actionpack (6.1.3.2) lib/action_dispatch/routing/route_set.rb:842:in `call'
railties (6.1.3.2) lib/rails/engine.rb:539:in `call'
railties (6.1.3.2) lib/rails/railtie.rb:207:in `public_send'
railties (6.1.3.2) lib/rails/railtie.rb:207:in `method_missing'
actionpack (6.1.3.2) lib/action_dispatch/routing/mapper.rb:20:in `block in <class:Constraints>'
actionpack (6.1.3.2) lib/action_dispatch/routing/mapper.rb:49:in `serve'
actionpack (6.1.3.2) lib/action_dispatch/journey/router.rb:50:in `block in serve'
actionpack (6.1.3.2) lib/action_dispatch/journey/router.rb:32:in `each'
actionpack (6.1.3.2) lib/action_dispatch/journey/router.rb:32:in `serve'
actionpack (6.1.3.2) lib/action_dispatch/routing/route_set.rb:842:in `call'
lib/middleware/omniauth_bypass_middleware.rb:71:in `call'
rack (2.2.3) lib/rack/tempfile_reaper.rb:15:in `call'
rack (2.2.3) lib/rack/conditional_get.rb:27:in `call'
rack (2.2.3) lib/rack/head.rb:12:in `call'
actionpack (6.1.3.2) lib/action_dispatch/http/permissions_policy.rb:22:in `call'
lib/content_security_policy/middleware.rb:12:in `call'
lib/middleware/anonymous_cache.rb:355:in `call'
config/initializers/008-rack-cors.rb:25:in `call'
rack (2.2.3) lib/rack/session/abstract/id.rb:266:in `context'
rack (2.2.3) lib/rack/session/abstract/id.rb:260:in `call'
actionpack (6.1.3.2) lib/action_dispatch/middleware/cookies.rb:689:in `call'
actionpack (6.1.3.2) lib/action_dispatch/middleware/callbacks.rb:27:in `block in call'
activesupport (6.1.3.2) lib/active_support/callbacks.rb:98:in `run_callbacks'
actionpack (6.1.3.2) lib/action_dispatch/middleware/callbacks.rb:26:in `call'
actionpack (6.1.3.2) lib/action_dispatch/middleware/actionable_exceptions.rb:18:in `call'
actionpack (6.1.3.2) lib/action_dispatch/middleware/debug_exceptions.rb:29:in `call'
actionpack (6.1.3.2) lib/action_dispatch/middleware/show_exceptions.rb:33:in `call'
logster (2.9.6) lib/logster/middleware/reporter.rb:43:in `call'
railties (6.1.3.2) lib/rails/rack/logger.rb:37:in `call_app'
railties (6.1.3.2) lib/rails/rack/logger.rb:28:in `call'
config/initializers/100-quiet_logger.rb:23:in `call'
config/initializers/100-silence_logger.rb:31:in `call'
actionpack (6.1.3.2) lib/action_dispatch/middleware/remote_ip.rb:81:in `call'
actionpack (6.1.3.2) lib/action_dispatch/middleware/request_id.rb:26:in `call'
lib/middleware/enforce_hostname.rb:23:in `call'
plugins/discoursehosting-features/plugin.rb:28:in `call'
rack (2.2.3) lib/rack/method_override.rb:24:in `call'
rack (2.2.3) lib/rack/sendfile.rb:110:in `call'
actionpack (6.1.3.2) lib/action_dispatch/middleware/host_authorization.rb:92:in `call'
rack-mini-profiler (2.3.2) lib/mini_profiler/profiler.rb:249:in `call'
message_bus (3.3.5) lib/message_bus/rack/middleware.rb:61:in `call'
lib/middleware/request_tracker.rb:177:in `call'
rails_multisite (3.0.0) lib/rails_multisite/middleware.rb:25:in `call'
plugins/discoursehosting-features/plugin.rb:46:in `call'
railties (6.1.3.2) lib/rails/engine.rb:539:in `call'
railties (6.1.3.2) lib/rails/railtie.rb:207:in `public_send'
railties (6.1.3.2) lib/rails/railtie.rb:207:in `method_missing'
rack (2.2.3) lib/rack/urlmap.rb:74:in `block in call'
rack (2.2.3) lib/rack/urlmap.rb:58:in `each'
rack (2.2.3) lib/rack/urlmap.rb:58:in `call'
unicorn (6.0.0) lib/unicorn/http_server.rb:634:in `process_client'
unicorn (6.0.0) lib/unicorn/http_server.rb:732:in `worker_loop'
unicorn (6.0.0) lib/unicorn/http_server.rb:547:in `spawn_missing_workers'
unicorn (6.0.0) lib/unicorn/http_server.rb:561:in `maintain_worker_count'
unicorn (6.0.0) lib/unicorn/http_server.rb:294:in `join'
unicorn (6.0.0) bin/unicorn:128:in `<top (required)>'
vendor/bundle/ruby/2.7.0/bin/unicorn:23:in `load'
vendor/bundle/ruby/2.7.0/bin/unicorn:23:in `<main>'
vendor/bundle/ruby/2.7.0/bin/ruby_executable_hooks:24:in `eval'
vendor/bundle/ruby/2.7.0/bin/ruby_executable_hooks:24:in `<main>'
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