This message appears in the logs every time a trollager attacks.
https://gist.github.com/NotAVerb/8d85605dedefb9ab263db617beb6d269

Just did a quick test with only PrimitiveMobs installed. The error is the same.

Strange.... thanks for reporting. Will take a look. Could it be that you have a mod that changes the breaking block particle somehow? Or maybe some block is somehow seen as Air... hmmst

Thanks for testing, will take a look at this

Fixed in the next version