fix: table preview

@@ -11,6 +11,9 @@ import (
 )
 )
 
 
 func (tableService *TableService) TablePreview(ctx *domain.Context, cmd *command.TablePreviewCommand) (interface{}, error) {
 func (tableService *TableService) TablePreview(ctx *domain.Context, cmd *command.TablePreviewCommand) (interface{}, error) {
+	if cmd.TableId == 0 {
+		return &dto.TablePreviewDto{}, nil
+	}
 	if err := cmd.ValidateCommand(); err != nil {
 	if err := cmd.ValidateCommand(); err != nil {
 		return nil, application.ThrowError(application.ARG_ERROR, err.Error())
 		return nil, application.ThrowError(application.ARG_ERROR, err.Error())
 	}
 	}

@@ -278,6 +278,9 @@ func (ptr *QuerySetService) PreviewPrepare(ctx *domain.Context, querySetId int,
 			return t, nil
 			return t, nil
 		}
 		}
 	}
 	}
+	if len(queryComponents) == 0 {
+		return &domain.Table{}, nil
+	}
 
 
 	// 验证
 	// 验证
 	if err = ptr.validQueryComponents(queryComponents); err != nil {
 	if err = ptr.validQueryComponents(queryComponents); err != nil {