Description of problem:

Currently when the URL points to a plugin page that is not available, meaning no such a catalog entity for the plugin, the side drawer shows a compiler TypeError which is not expected. We should improve this behavior to show a proper user friendly message.

Version-Release number of selected component (if applicable):

release 1.5 - release 1.7 - main branch

How reproducible:

Enable Extensions plugin and start your local RHDH by `yarn dev`

Steps to Reproduce:

1. Attach this example url to see the compiler error

localhost:3001/extensions/plugins/rhdh/backstage-community-plugin-tech-radar

key point: `backstage-community-plugin-tech-radar` is a package name not a plugin name, which means there's no plugin entity for such name, and there's no plugin info available for the side drawer display

Actual results:

See attached screenshot

Expected results:

User friendly error message, stating that this plugin is not available, please check your plugin's catalog entity. Or message similar to this.

Additional info: