Crash on using death's bite

In version 0.0.35, I equipped a death’s bite onto my berserker frog and attacked. The frog did full damage, then did full damage again, then the game crashed with the below. I did manage to make it though one full battle without a crash.


############################################################################################
FATAL ERROR in
action number 1
of Step Event0
for object obj_battlecontroller:

Variable obj_artifact.(100141, -2147483648) not set before reading it.
at gml_Script_bc_ExecuteEvents
############################################################################################

stack frame is
gml_Script_bc_ExecuteEvents (line 0)
gml_Object_obj_battlecontroller_Step_0

Happened again after a few more battles.


############################################################################################
FATAL ERROR in
action number 1
of Step Event0
for object obj_battlecontroller:

Variable obj_artifact.(100141, -2147483648) not set before reading it.
at gml_Script_bc_ExecuteEvents
############################################################################################

stack frame is
gml_Script_bc_ExecuteEvents (line 0)
gml_Object_obj_battlecontroller_Step_0