WikiController raises a undefined method custom_workflow_messages' for #<WikiContentVersion:0x00007f7b45c567d8> error if @content` assigned to the WikiContentVersion. Since plugin doesn't support WikiContentVersion just skip it.

lib/redmine_custom_workflows/patches/controllers/wiki_controller_patch.rb

@@ -73,7 +73,9 @@ module RedmineCustomWorkflows
           elsif @page
             objects = [@page]
           end
-          if @content
+          # @content either WikiContent or WikiContentVersion
+          # but plugin does not patch nor work with WikiContentVersion
+          if @content.is_a? WikiContent
             objects ||= []
             objects << @content
           end