Fix redrafting a currently-editing post not leaving edit mode (#20023)

app/javascript/mastodon/reducers/compose.js

@@ -452,6 +452,7 @@ export default function compose(state = initialState, action) {
       map.set('idempotencyKey', uuid());
       map.set('sensitive', action.status.get('sensitive'));
       map.set('language', action.status.get('language'));
+      map.set('id', null);
 
       if (action.status.get('spoiler_text').length > 0) {
         map.set('spoiler', true);