gmain: Avoid checking for context value in internal function

This is something that is supposed to do by the public API, as everywhere
else the internal functions should be called with proper parameters instead

glib/gmain.c

@@ -3605,9 +3605,6 @@ g_main_context_wait_internal (GMainContext *context,
   GThread *self = G_THREAD_SELF;
   gboolean loop_internal_waiter;
   
-  if (context == NULL)
-    context = g_main_context_default ();
-
   loop_internal_waiter = (mutex == &context->mutex);
   
   if (!loop_internal_waiter)