Add validation warning for unsquare buildings

modules/core/history.js

@@ -155,6 +155,8 @@ export function coreHistory(context) {
                     })
                     .on('end interrupt', function() {
                         _overwrite(origArguments, 1);
+                        // run the completion handler, if any
+                        if (action0.onCompletion) action0.onCompletion();
                     });
 
             } else {