Fix broken ProgressBarMessage after 8f596e29b3

src/guiengine/message_queue.cpp

@@ -302,6 +302,7 @@ public:
     ProgressBarMessage(const core::stringw& msg) :
                Message(9999999.9f, msg)
     {
+        m_swc.m_next = new SkinWidgetContainer;
     }   // ProgressBarMessage
     // ------------------------------------------------------------------------
     ~ProgressBarMessage()                             { g_progress.store(-1); }