patch 8.2.1117: Coverity warns for unsing unitialized field

Problem:    Coverity warns for unsing unitialized field.
Solution:   Initialize v_lock.
diff --git a/src/if_lua.c b/src/if_lua.c
index 20cdbbc..9852c61 100644
--- a/src/if_lua.c
+++ b/src/if_lua.c
@@ -576,6 +576,8 @@
 {
     int status = OK;
 
+    tv->v_lock = 0;
+
     switch (lua_type(L, pos))
     {
 	case LUA_TBOOLEAN: