Only purge files that are already persisted

The reasons for that being the case can be vast, but it does not make
sense to purge things that are not persisted.

Author: kronn

lib/nochmal/adapters/carrierwave_analyze.rb

@@ -92,7 +92,7 @@ def active_storage_change(type, uploader)
             # allow removal, carrierwave-style
             def remove_#{type}; false end
             def remove_#{type}=(deletion_param)
-              if %w(1 yes true).include?(deletion_param.to_s.downcase)
+              if %w(1 yes true).include?(deletion_param.to_s.downcase) && #{type}.persisted?
                 #{type}.purge_later
               end
             end