Trying to recreate spikes that move when jumping

[DemoTou]

Hey,

I'm currently trying to recreate spikes that go up and down whenever you jump like in Boshy.
I found this post https://iwannacommunity.com/forum/index.php?topic=2390.msg17113#msg17113
and did everything that was written there but I get this error. (I'm using Game Maker Studio 1.4.1)

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

Push :: Execution Error - Variable Get 102128.tX(100224, -2147483648)
 at gml_Object_objJumpspikeUp_StepNormalEvent_1 (line 12) -     x=lerp(sX,tX,sine);
############################################################################################

I hope someone can help me figure out where the problem is.