After about an hour or so of gameplay my game will just start repeatedly crashing does anyone know why?

The crash code is this:

___________________________________________
############################################################################################
FATAL ERROR in
action number 1
of Mouse Event for Left Pressed
for object objRingMenuItem:

Push :: Execution Error - Variable Index [20,0] out of range [20,-1] - 3.<unknown variable>(100048,640000)
at gml_Script_RemoveItem
############################################################################################
--------------------------------------------------------------------------------------------
stack frame is
gml_Script_RemoveItem (line 0)
gml_Object_objRingMenuItem_Mouse_4