If the bundle is disabled (ie: enabled: false), don't validate the dsn parameter

[j0k3r]

In recents commit, you introduced the enabled (and/or the dsn) option.
But if we don't enable the plugin, it still wants to validate the dsn parameter.

The path "kunstmaan_sentry.dsn" cannot contain an empty value, but got null.

If we set :

kunstmaan_sentry:
    enabled: false

You shouldn't try to validate other parameters since it is not enabled.
Or at least, you should allow :

kunstmaan_sentry:
    enabled: false
    dsn: null

Or

kunstmaan_sentry:
    enabled: false
    dsn: ''