Avoid attaching a menu to the BMenuWindow when not needed

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@16863 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/kits/interface/Menu.cpp

@@ -1606,7 +1606,7 @@ BMenu::MenuWindow()
 	if (fCachedMenuWindow == NULL) {
 		char windowName[64];
 		snprintf(windowName, 64, "%s cached menu", Name());
-		fCachedMenuWindow = new BMenuWindow(windowName, this);
+		fCachedMenuWindow = new BMenuWindow(windowName, NULL);
 	}
 
 	return fCachedMenuWindow;

src/kits/interface/MenuWindow.cpp

@@ -38,7 +38,8 @@ BMenuWindow::BMenuWindow(const char *name, BMenu *menu)
 	fUpperScroller(NULL),
 	fLowerScroller(NULL)
 {
-	SetMenu(menu);
+	if (menu != NULL)
+		SetMenu(menu);
 }