15:41:19 [INFO] [OtherDrops:2.8b.156] EntityDamageEvent: tool is null, please inform developer.

No more info is provided in the error :/

Thanks for that. I've modified the message to only appear now if it's not TNT related (as tnt often wont have a "tool" as such). Closing the issue - please open a new one if the message re-appears.