fix(Plugin): add missing binding to sprite cleanup function

[liorcode]

When using multiple instances of the plugin, each instance will delete sprite created by the previous one.

This is due to a missing "this" binding for the cleanup callback. Without the binding, the "this" is the the same one for each iteration.

[mixtur]

Ouch. I guess I am too used to use arrow functions.

[mixtur]

I'll publish it later today.

[liorcode]

yeah, it is hard to use regular function these days :)
thanks!