Selecting game already open in a tab brings user to that tab. (#4653)

* When trying to join a game from GameSelector that's already been joined by you, navigate to its game tab.

* return immediately, do not change button states

Co-authored-by: ebbit1q <ebbit1q@gmail.com>

cockatrice/src/tab_supervisor.cpp

@@ -735,3 +735,16 @@ const ServerInfo_User *TabSupervisor::getOnlineUser(const QString &userName) con
 
     return nullptr;
 };
+
+bool TabSupervisor::switchToGameTabIfAlreadyExists(const int gameId)
+{
+    bool isGameTabExists = false;
+    if (gameTabs.contains(gameId)) {
+        isGameTabExists = true;
+        TabGame *tabGame = gameTabs[gameId];
+        const int gameTabIndex = indexOf(tabGame);
+        setCurrentIndex(gameTabIndex);
+    }
+
+    return isGameTabExists;
+}