gqueue: Remove a redundant branch

queue->tail->next cannot be non-NULL, as pushing onto the end of the
queue is handled by the call to g_queue_push_tail_link() above.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

glib/gqueue.c

@@ -519,8 +519,10 @@ g_queue_push_nth_link (GQueue *queue,
   if (queue->head->prev)
     queue->head = queue->head->prev;
 
-  if (queue->tail->next)
-    queue->tail = queue->tail->next;
+  /* The case where we’re pushing @link_ at the end of @queue is handled above
+   * using g_queue_push_tail_link(), so we should never have to manually adjust
+   * queue->tail. */
+  g_assert (queue->tail->next == NULL);
   
   queue->length++;
 }