Chained call event-loc block returns an error if no loc block exists.

If you try to get an event and its loc block with a chained call, like this:

$result = civicrm_api3('Event', 'getsingle', array(
'sequential' => 1,
'return' => "title,loc_block_id",
'id' => 1000,
'api.LocBlock.get' => array('id' => "\$value.loc_block_id"),
));

the API returns an error if the event doesn't have a loc block:

{ "error_field":"id", "type":"integer", "error_code":2001, "entity":"Event", "action":"get", "is_error":1, "error_message":"Error in call to LocBlock_get : id is not a valid integer" }

See also this forum thread: http://forum.civicrm.org/index.php/topic,36113.0.html