PreviewInput/ProgramInput nil on "connected" event

[chxmbley]

Occasionally, atem.emit panics with signal SIGSEGV: segmentation violation due to the .Call(in) at this line

[chxmbley]

Actually, .Call is at the bottom of the stack trace. This is the line at the top of the trace 😕

[chxmbley]

Problem was caused by atem.ProgramInput occasionally being nil. Added a check in 95b9f33 to catch this.

[bdogan]

On "connected" event program or preview input must not actually be nil. I will check it later