I cannot reproduce this error; how did you create this? :) Do you have any other extensions loaded? If yes, can you test without the other extensions, too? (EDIT: I see in your logs that you used other extensions; so, it may be that my extension is incompatible with someone else's. Maybe with better combat effects by rhagelstrom)
Also: In case you use FG unity, then use the version from the forge:
https://forge.fantasygrounds.com/shop/items/31/view :) If you use the version attached here in the forums, then you may get an error, I am not sure; the version in the forum is only for FG classic :)