Actions performed (e.g. adding midpoint) must trigger validation

(re: #8655)

modules/modes/select.js

@@ -429,11 +429,14 @@ export function modeSelect(context, selectedIDs) {
                     actionAddMidpoint({ loc: choice.loc, edge: [prev, next] }, osmNode()),
                     t('operations.add.annotation.vertex')
                 );
+                context.validator().validate();
 
             } else if (entity.type === 'midpoint') {
                 context.perform(
                     actionAddMidpoint({ loc: entity.loc, edge: entity.edge }, osmNode()),
-                    t('operations.add.annotation.vertex'));
+                    t('operations.add.annotation.vertex')
+                );
+                context.validator().validate();
             }
         }
 
@@ -688,6 +691,7 @@ export function modeSelect(context, selectedIDs) {
             // the user added this relation but didn't edit it at all, so just delete it
             var deleteAction = actionDeleteRelation(entity.id, true /* don't delete untagged members */);
             context.perform(deleteAction, t('operations.delete.annotation.relation'));
+            context.validator().validate();
         }
     };