« MODx Parse Error »

MODx encountered the following error while attempting to parse the requested resource:
« Execution of a query to the database failed - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'ORDER BY t1.Id' at line 1 »
      SQL: SELECT SQL_CALC_FOUND_ROWS t1.Id, t1.title, t1.description, t1.main_img FROM db_documents AS t1 LEFT JOIN vs_tags_docs AS t2 ON t1.Id = t2.doc WHERE t2.tag = ORDER BY t1.Id
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Parser timing
  MySQL: 0.0033 s(1 Requests)
  PHP: 0.0165 s 
  Total: 0.0199 s