revid-cli: crashes in NetSender mode with RTMP output

[Alan Noble]

This happens when -NetSender is specified on the command line with no other command-line flags, i.e., all vars are pulled from NetReceiver.

Relevant stack trace:

goroutine 1 [running]: bitbucket.org/ausocean/av/revid.(*Revid).Update(0x2401880, 0x2445960, 0x0, 0x0) /home/pi/go/src/bitbucket.org/ausocean/av/revid/revid.go:405 +0x1744 main.run(0x0, 0x0, 0x0, 0x0, 0x800, 0x0, 0x0, 0x0, 0x0, 0x0, ...) /home/pi/go/src/bitbucket.org/ausocean/av/cmd/revid-cli/main.go:285 +0x10c main.main() /home/pi/go/src/bitbucket.org/ausocean/av/cmd/revid-cli/main.go:105 +0xf4

[Alan Noble]

Additional info obtained from adding NetReceiver vars one by one:

1) Adding RtmpUrl set to the YouTube URL is OK.

2) Adding HorizontalFlip and VerticalFlip both set to Yes results in the following warning:

{"level":"warn","time":"2019-02-24T23:40:18.279Z","caller":"revid/revid.go:476","message":"revid:invalid HorizontalFlip param","value":"Yes"}

3) Adding Output set to Rtmp causes the crash.

[Saxon Milton]

Resolved in PR #153