Cannot add mailing list recipient to group node once it has already created

One of my users discovered a bug in og2list (both HEAD and 4.7 branches). There is no code in hook_nodeapi() when $op='update' to process the 'recipient' ($node->og2list_ml) value, but the text box to enter it still appears when a node does not have a recipient set yet.

The attached patch goes into og2list_nodeapi() right after case 'update':

case 'update':
      /* If the node previously did not have an address and one has just been assigned,
       * then we need to set it now.  If the node did have an og2list_groups row before
       * then the recipient wasn't set and we update it.  For now you still cannot change
       * a recipient once it's set. 
       */
      if ($node->recipient && 
           (db_num_rows(db_query("SELECT recipient FROM {og2list_groups} WHERE nid = %d",$node->nid)) == 0)) {	 	  	  
        db_query("INSERT INTO {og2list_groups} (nid, recipient, status) "
                  . " VALUES(%d, '%s', 1)", $node->nid, $node->recipient);
      }	
 // existing update logic continues here

This allows the Mailing List Address field to be filled in if a list has not been set yet, but prevents og2list trying to insert it when the row already exists (and $node->recipient is a hidden value containing its address).

The attached patch is for HEAD. It should also apply to 4.7 but I'll attach a backported patch for DRUPAL-4-7 in a comment.