fix: dm Database Clob field conversion error (#2405)

Reviewed-on: https://gitea.com/xorm/xorm/pulls/2405
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: zzdboy <28206697@qq.com>
Co-committed-by: zzdboy <28206697@qq.com>

dialects/dameng.go

@@ -831,6 +831,13 @@ func (d *dmClobScanner) Scan(data interface{}) error {
 		d.data = string(t)
 		d.valid = true
 		return nil
+	case string:
+		if len(t) <= 0 {
+			return nil
+		}
+		d.data = string(t)
+		d.valid = true
+		return nil
 	default:
 		return fmt.Errorf("cannot convert %T as dmClobScanner", data)
 	}