patch 8.2.2486: Vim9: some errors for white space do not show context

Problem:    Vim9: some errors for white space do not show context.
Solution:   Include the text at the error.
diff --git a/src/list.c b/src/list.c
index c93a66d..4d33aa6 100644
--- a/src/list.c
+++ b/src/list.c
@@ -1328,7 +1328,8 @@
 	    if (do_error)
 	    {
 		if (**arg == ',')
-		    semsg(_(e_no_white_space_allowed_before_str), ",");
+		    semsg(_(e_no_white_space_allowed_before_str_str),
+								    ",", *arg);
 		else
 		    semsg(_("E696: Missing comma in List: %s"), *arg);
 	    }