raidboss: fix error if TriggerParams are undefined (#4525)
raidboss: fix error if TriggerParams are undefined (#4525)

This was changed in #4449, but the incorrect typing obscured
that this was possible.  Type assertions hiding bugs.  :C
quisquous/cactbot,quisquous/cactbot,quisquous/cactbot,quisquous/cactbot,quisquous/cactbot,quisquous/cactbot