On line 433 and 437 of ezsubtreenotificationrule.php there is a php function call array_intersect() which awaiting to arrays for comparison and determination of the intersection of both arrays.
But in both cases it will be passed with a String (ownerID and contentobjectID -> I think attribute owner ID and contentobjectID could never be an array).
This can not be work and smashes a php warning.

Change to in_array instead.