In awt_MToolkit.c, function awt_MToolkit_loop did *not* check whether
the call to XtAppPeekEvent returned True or False. A True return value
indicates that it found an X event on the queue, a False value that it
did not. But if it returned False, this code went ahead and switched on
the event type in xev.type anyway, which may contain garbage on the stack.
In that case, the execution of this switch was unsafe and unpredictable.