patch 9.0.0345: error message for list argument could be clearer

Problem:    Error message for list argument could be clearer.
Solution:   Include the argument number. (Yegappan Lakshmanan, closes #11027)
diff --git a/src/list.c b/src/list.c
index 5e70f21..c9697e0 100644
--- a/src/list.c
+++ b/src/list.c
@@ -1519,11 +1519,8 @@
 		|| check_for_opt_string_arg(argvars, 1) == FAIL))
 	return;
 
-    if (argvars[0].v_type != VAR_LIST)
-    {
-	emsg(_(e_list_required));
+    if (check_for_list_arg(argvars, 0) == FAIL)
 	return;
-    }
 
     if (argvars[0].vval.v_list == NULL)
 	return;
@@ -1728,11 +1725,8 @@
 		|| check_for_opt_bool_arg(argvars, 1) == FAIL))
 	return;
 
-    if (argvars[0].v_type != VAR_LIST)
-    {
-	emsg(_(e_invalid_argument));
+    if (check_for_list_arg(argvars, 0) == FAIL)
 	return;
-    }
 
     l = argvars[0].vval.v_list;
     if (l == NULL)