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/textprop.c b/src/textprop.c
index de3344f..5f5c6a2 100644
--- a/src/textprop.c
+++ b/src/textprop.c
@@ -348,11 +348,8 @@
 	    || check_for_list_arg(argvars, 1) == FAIL)
 	return;
 
-    if (argvars[1].vval.v_list == NULL)
-    {
-	emsg(_(e_list_required));
+    if (check_for_nonnull_list_arg(argvars, 1) == FAIL)
 	return;
-    }
 
     dict = argvars[0].vval.v_dict;
     if (dict == NULL || !dict_has_key(dict, "type"))