Small improvements

Author: lunny

models/user/user.go

@@ -856,6 +856,10 @@ func GetUserByID(ctx context.Context, id int64) (*User, error) {
 
 // GetUserByIDs returns the user objects by given IDs if exists.
 func GetUserByIDs(ctx context.Context, ids []int64) ([]*User, error) {
+	if len(ids) <= 0 {
+		return nil, nil
+	}
+
 	users := make([]*User, 0, len(ids))
 	err := db.GetEngine(ctx).In("id", ids).
 		Table("user").