patch 8.2.1326: Vim9: skipping over white space after list

Problem:    Vim9: skipping over white space after list.
Solution:   Do not skip white space, a following [] would be misinterpreted.
            (closes #6552)  Fix a few side effects.
diff --git a/src/list.c b/src/list.c
index 9a334ae..5c2f60e 100644
--- a/src/list.c
+++ b/src/list.c
@@ -1199,7 +1199,7 @@
 	had_comma = **arg == ',';
 	if (had_comma)
 	{
-	    if (vim9script && (*arg)[1] != NUL && !VIM_ISWHITE((*arg)[1]))
+	    if (vim9script && !IS_WHITE_OR_NUL((*arg)[1]))
 	    {
 		semsg(_(e_white_after), ",");
 		goto failret;
@@ -1231,7 +1231,7 @@
 	return FAIL;
     }
 
-    *arg = skipwhite(*arg + 1);
+    *arg += 1;
     if (evaluate)
 	rettv_list_set(rettv, l);