Hi,
That's odd. I tried on 5.3 and 5.4 but this line doesn't cause any trouble.
Which version of Unity are you using?
As Alex mentionned, none of this is part of PlayMaker asset package you downloaded from the Unity Asset store, so it was installed either from the wiki, the forum or the Ecosystem, or else it was already there in your project before you upgraded Unity.
Can you paste the first error you get in the Unity console, as well as the last error. Something else is playing funny which causes a chain reaction for other scripts to loose it.
Bye,
Jean