Check if ActiveRecord connection exists before calling AR connection …

…pool

sentry-rails/lib/sentry/rails/background_worker.rb

@@ -1,8 +1,13 @@
 module Sentry
   class BackgroundWorker
     def _perform(&block)
-      # make sure the background worker returns AR connection if it accidentally acquire one during serialization
-      ActiveRecord::Base.connection_pool.with_connection do
+      # some applications have partial or even no AR connection
+      if ActiveRecord::Base.connected?
+        # make sure the background worker returns AR connection if it accidentally acquire one during serialization
+        ActiveRecord::Base.connection_pool.with_connection do
+          block.call
+        end
+      else
         block.call
       end
     end