Reduce console errors (UNTESTED)

[LaytonGB]

I'm getting errors in the console that aren't actually problems. This should silence the errors.

Errors:

turnmarker.js:56 Uncaught (in promise) TypeError: Cannot read property 'token' of undefined
    at turnmarker.js:56
    at Function._call (foundry.js:2239)
    at Function.call [as __furnace_original_call] (foundry.js:2224)
    at Function.callOriginalFunction (Patches.js:57)
    at Function.<anonymous> (Debug.js:42)
    at foundry.js:10265
    at Array.reduce (<anonymous>)
    at Scene.updateEmbeddedEntity (foundry.js:10253)
    at Token.update (foundry.js:12053)
    at DragRuler.moveToken (showdragdistance.js:323)

Fixes #12