I just copied it as is, I tried to roll right before landing on the ground and got this sorry
___________________________________________
############################################################################################
FATAL ERROR in
action number 1
of Step Event0
for object oPlayer:
Variable oPlayer.soStepGrass(100567, -2147483648) not set before reading it.
at gml_Object_oPlayer_Step_0
############################################################################################
--------------------------------------------------------------------------------------------
stack frame is
gml_Object_oPlayer_Step_0 (line -1)