fix bug so that doc_length also deletes documents that dtm deletes
fix bug so that doc_length also deletes documents that dtm deletes

mgree/sigplan,mgree/sigplan,mgree/tmpl,mgree/sigplan,mgree/tmpl,mgree/tmpl,mgree/tmpl,mgree/tmpl,mgree/sigplan,mgree/sigplan,mgree/tmpl,mgree/sigplan