DTMF: fix the issue where "#", "*" will not be responded for the first key press

- issues occurs when the first pressed key is shift,
  and key_pressed is set, the second key pressed will be
  returned.

Change-Id: Ie71f8f6aaf9ae6211562f60c4fe2c9e67f1ba49b

src/ringmainwindow.cpp

@@ -666,8 +666,9 @@ on_dtmf_pressed(RingMainWindow* self, GdkEventKey* event, gpointer user_data)
     g_return_val_if_fail(IS_RING_MAIN_WINDOW(self), GDK_EVENT_PROPAGATE);
     auto* priv = RING_MAIN_WINDOW_GET_PRIVATE(RING_MAIN_WINDOW(self));
 
-    if(priv->key_pressed)
+    if(priv->key_pressed && !(event->state & GDK_SHIFT_MASK)){
         return GDK_EVENT_PROPAGATE;
+    }
 
     (void)user_data;