patch 9.0.0499: in :def function list created after const is locked

Problem:    In :def function list created after const is locked.
Solution:   Reset v_lock. (closes #11154)
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 22dfaaa..c2a3310 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -200,6 +200,7 @@
     tv = STACK_TV_BOT(-1);
     tv->v_type = VAR_LIST;
     tv->vval.v_list = list;
+    tv->v_lock = 0;
     if (list != NULL)
 	++list->lv_refcount;
     return OK;