Wikimedia Bugzilla is closed!

I was trying to edit the header of Talk:Flow for the first time. But someone else had snuck in and created the header while I was editing.  The result of [Preview] or [Save header] is an errorbox

   "An error occurred.
   The error message received was: Previous revision identifier is missing."

the failing API call is:

{"warnings":{"main":{"*":"Unrecognized parameter: 'workflowId'"}},"flow":{"edit-header":{"result":"error","errors":{"header":{"prev_revision":"Previous revision identifier is missing."}}}}}

(The message would be different if the header already existed and there was an edit conflict.)

The workaround is to reload the page and then edit the page. The fix is edit conflict handling.