Fix: file size is ready dirty when clean upload sessions

After listing to be deleted files, before delete is committed to database, file size might be changed by ongoing upload, causing inconsistent user storage.

models/file.go

@@ -221,14 +221,17 @@ func DeleteFiles(files []*File, uid uint) error {
 	for _, file := range files {
 		if file.UserID != uid {
 			tx.Rollback()
-			return errors.New("User id not consistent")
+			return errors.New("user id not consistent")
 		}
 
-		result := tx.Unscoped().Delete(file)
-		if result.RowsAffected != 0 {
-			size += file.Size
+		result := tx.Unscoped().Where("size = ?", file.Size).Delete(file)
+		if result.RowsAffected == 0 {
+			tx.Rollback()
+			return errors.New("file size is dirty")
 		}
 
+		size += file.Size
+
 		if result.Error != nil {
 			tx.Rollback()
 			return result.Error