patch 9.1.1333: Coverity: complains about unutilized variable

Problem:  Coverity: complains about unutilized variable
Solution: initialize typval properly
          (author)

Fixes: Coverity issue: 1646573
       tmp.v_lock is left unitialized
related: #17189

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/typval.c b/src/typval.c
index b9f8f1c..db439cb 100644
--- a/src/typval.c
+++ b/src/typval.c
@@ -1305,6 +1305,7 @@
     {
 	typval_T tmp;
 
+	init_tv(&tmp);
 	f_string(varp, &tmp);
 	tv_get_string_buf(&tmp, buf);
 	clear_tv(varp);