patch 9.0.1569: cannot use "this.member" in lambda in class method

Problem:    Cannot use "this.member" in lambda in class method.
Solution:   Adjust check for reserved keyword. (Hirohito Higashi,
            closes #12416, closes #12076, closes #12336)
diff --git a/src/eval.c b/src/eval.c
index bae7280..b8d954d 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1654,7 +1654,7 @@
     {
 	cc = *endp;
 	*endp = NUL;
-	if (in_vim9script() && check_reserved_name(lp->ll_name, NULL) == FAIL)
+	if (in_vim9script() && check_reserved_name(lp->ll_name, FALSE) == FAIL)
 	    return;
 
 	if (lp->ll_blob != NULL)