Enforce uniqueness causes error "in_array() expects parameter 2 to be array"

I am adding an item to a list and have "Enforce uniqueness" enabled. This gives me an error:

Warning: in_array() expects parameter 2 to be array, null given in rules_condition_data_list_contains() (line 359 of \sites\all\modules\rules\modules\data.eval.inc).

Adding an initial value to the "list" or disabling "Enforce uniqueness" causes this error to stop. I think its erroring because the array is empty.

Line 359 says:

  return in_array($item, $list);

I think it should probably be:

  return empty($list) ? FALSE : in_array($item, $list);