That's funny. I thought maybe the nightly might force you to define the hit animation, but only working when you don't have it is weird. Maybe lasers aren't a proper hit animation in the nightly for explosions?
Actually, in 1.0, giving it a blast radius overwrote the hit animation and I got a regular explosion, despite it being supposed to be the laser hit animation (hitAnimation: 36). Maybe in the nightly, if you ask for the laser, it does try to do the laser animation, but it doesn't work for explosions since it's a bullet hit, so it crashes..?
All area of effect attacks in 1.0 are restricted to be regular explosions. The nightly does have definable explosion animations, to be able to support TFTD with underwater and above water combat, which 1.0 does not have. You could try to define "hitAnimation: 0" in the nightly, which just requests the regular explosion, and see if it works.