Always return true when sorting a null queue

Author: YuShuanHsieh

qtest.c

@@ -485,6 +485,8 @@ bool do_sort(int argc, char *argv[])
     exception_cancel();
     set_noallocate_mode(false);
 
+    if (q == NULL)
+        return true;
     list_ele_t *e = q->head;
     bool ok = true;
     while (ok && e && --cnt) {