GANG: Show error popup when there are errors

[catloversg]

This PR makes 2 changes:

• Remove the useless check isNaN(numCycles):
  • process is only called from src\engine.tsx. I checked its callers. numCycles cannot be invalid.
  • If numCycles is invalid, that check only prints to the console without doing anything else. It's useless anyway.
• When there are errors while processing gang data, show an error popup instead of printing to the console.

[d0sboots]

Since this is a popup, won't it end up popping up every 200ms, thus making gameplay impossible?

I'm all for surfacing error messages better, but I feel like there needs to be a middle ground here.

[d0sboots]

Great!