SQL error if node has no term from vocabularies

I encountered an error with a node which had no taxonomy associations to any of the terms in the configured vocabularies. For some reason, Drupal 5.7 gives an empty $term in this case in your foreach of $node->taxonomy in _tac_lite_get_terms(). The attached patch makes sure to only add the $term if it is indeed something positive (not an empty string as I experience).

Patch created from a local SVN copy but should apply just fine to the 5.x version.