patch 9.1.0197: Vim9: problem evaluating negated boolean logic

Problem:  Vim9: problem evaluating negated boolean logic
          (lxhillwind)
Solution: Don't clear the first value on short circuit evaluation
          (Yegappan Lakshmanan)

fixes: #14265
closes: #14269

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/vim9expr.c b/src/vim9expr.c
index ee9712b..9d67aea 100644
--- a/src/vim9expr.c
+++ b/src/vim9expr.c
@@ -2779,7 +2779,7 @@
     if (compile_subscript(arg, cctx, start_leader, &end_leader,
 							     ppconst) == FAIL)
 	return FAIL;
-    if (ppconst->pp_used > 0)
+    if ((ppconst->pp_used > 0) && (cctx->ctx_skip != SKIP_YES))
     {
 	// apply the '!', '-' and '+' before the constant
 	rettv = &ppconst->pp_tv[ppconst->pp_used - 1];