cleanup: Use consistent brace style of blocks

Our coding style has always been to either put braces around all
blocks, or avoid them for all. Fix the couple of places that slipped
through.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/731

js/ui/popupMenu.js

@@ -718,10 +718,11 @@ var PopupMenuBase = class {
                 this.disconnect(openStateChangeId);
                 menuItem.disconnect(destroyId);
             });
-        } else if (menuItem instanceof PopupBaseMenuItem)
+        } else if (menuItem instanceof PopupBaseMenuItem) {
             this._connectItemSignals(menuItem);
-        else
+        } else {
             throw TypeError("Invalid argument to PopupMenuBase.addMenuItem()");
+        }
 
         menuItem._setParent(this);