Fix harmless warning about a possibly uninitialized variable.

gcc complained about possibly uninitialized variable in QueueTestCase in
optimized build, just initialize it to suppress this warning.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64112 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

tests/thread/queue.cpp

@@ -174,7 +174,7 @@ void *QueueTestCase::MyThread::Entry()
     while ( messagesReceived < m_maxMsgCount )
     {
         wxMessageQueueError result;
-        int msg;
+        int msg = -1; // just to suppress "possibly uninitialized" warnings
 
         if ( m_type == WaitWithTimeout )
             result = m_queue.ReceiveTimeout(1000, msg);