500 error on dashboard listing with a custom YAML config

Summary

Steps to reproduce

1. Follow these instructions to setup Product Analytics in GDK.
2. View the dashboards list at Project > Analyze > Analytics dashboards and validate only Value Stream Dashboard is shown.
3. Add a custom YAML config for Value streams dashboard
4. Return to dashboards list - you will see the error
5. Enable the group_analytics_dashboards feature flag
6. View the dashboards list at Group > Analyze > Analytics dashboards - you will now see the error at the group level

What is the current bug behavior?

An error message is displayed

A JSON error is returned from the graphql query

{
    "errors": [
        {
            "message": "Internal server error: undefined method `parameterize' for nil:NilClass\n\n      @slug = slug.parameterize.underscore\n                  ^^^^^^^^^^^^^",
            "raisedAt": "/Users/vegito/glab/gdk/gitlab/ee/app/models/product_analytics/visualization.rb:101:in `initialize_with_error' \u003c-- /Users/vegito/glab/gdk/gitlab/ee/app/models/product_analytics/visualization.rb:106:in `initialize' \u003c-- /Users/vegito/glab/gdk/gitlab/ee/app/models/product_analytics/visualization.rb:67:in `new' \u003c-- /Users/vegito/glab/gdk/gitlab/ee/app/models/product_analytics/visualization.rb:67:in `load_visualization_data' \u003c-- /Users/vegito/glab/gdk/gitlab/ee/app/models/product_analytics/visualization.rb:71:in `load_product_analytics_visualization' \u003c-- /Users/vegito/glab/gdk/gitlab/ee/app/models/product_analytics/visualization.rb:92:in `from_data' \u003c-- /Users/vegito/glab/gdk/gitlab/ee/app/models/product_analytics/panel.rb:24:in `initialize' \u003c-- /Users/vegito/glab/gdk/gitlab/ee/app/models/product_analytics/panel.rb:9:in `new' \u003c-- /Users/vegito/glab/gdk/gitlab/ee/app/models/product_analytics/panel.rb:9:in `block in from_data' \u003c-- /Users/vegito/glab/gdk/gitlab/ee/app/models/product_analytics/panel.rb:8:in `map' \u003c-- /Users/vegito/glab/gdk/gitlab/ee/app/models/product_analytics/panel.rb:8:in `from_data'"
        }
    ]
}

What is the expected correct behavior?

Relevant logs and/or screenshots

Output of checks

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes

Frontend changes frontend

• Correctly handle schema errors that are returned from GraphQL - Example response
• Display an alert / warning (might need some UX input on the MR

Backend changes backend - DONE (included in !143786 (merged))

Adding safe navigation for the slug field attributes seems to fix this

diff --git a/ee/app/models/product_analytics/visualization.rb b/ee/app/models/product_analytics/visualization.rb
index a276fd59cf16..fd4daa691935 100644
--- a/ee/app/models/product_analytics/visualization.rb
+++ b/ee/app/models/product_analytics/visualization.rb
@@ -98,7 +98,7 @@ def initialize_with_error(init_error, slug)
       @type = 'unknown'
       @data = {}
       @errors = [init_error]
-      @slug = slug.parameterize.underscore
+      @slug = slug&.parameterize&.underscore
     end
 
     def initialize(config:, slug:, init_error: nil)
@@ -115,7 +115,7 @@ def initialize(config:, slug:, init_error: nil)
       rescue Psych::Exception => e
         @errors = [e.message]
       end
-      @slug = slug.parameterize.underscore
+      @slug = slug&.parameterize&.underscore
       validate
     end