Named Scarabus Blaster killed self: quest unsolveable

[jaymon]

Received a quest to kill boss so-and-so who was a Scarabus Blaster. (along with another monster)

During the fight, the boss exploded itself, as Scarabus Blasters often do.
Since I did not kill the boss, the quest did not complete, however the boss is dead, and does not respawn, leaving an unsolveable quest.

This is in version 0.908