Make GLControl work on OS X

This isn’t the greatest solution, but at least it doesn’t require us to
reference WinForms in OpenTK and it works perfectly for what I’m using.
Fix potential exception that I was ignoring.

This can happen, so we should handle it
Update spacing and formatting to match existing style
Call the new code instead of leaving the old version untouched
Merge remote-tracking branch 'sappharad/develop' into develop