Freeze when coordinates are NaN

[Viza74]

I accidentally passed NaN's as coordinates for circfill, and the whole game/page freezed totally, so I had to close the page and reopen again (Granted, i'm not a web developer, so probably there is a nicer way to solve this...)

sprcp with the same NaN coordinates just not draws anything, but at least not freezes.

I only tried with circfill, I don't know what happens with the other drawing routines.

[pistacchio]

I'll handle values that are not numbers and ignore them.
Thanks again, you're submitting some very useful reports.

[pistacchio]

I gave it a try at fully sanitizing the input but, where you stress the engine a bit, it is too computationally expensive. Expecially checking for NaN is extremely time consuming, so I'll leave the issue open as enhancement till I figure out how to sanitize all the inputs without taxing the CPU too much.