Handle pipe error or disk full/error in bmdcapture push_packet()

[vincib]

In push_packet functions, the return code of av_interleaved_write_frame is ignored.

We don't know if the outfile is in a disk error, disk full, or pipe issue state. it seems you planned to do that by defining "ret" as an integer ;) This patch handle this case.

[lu-zero]

Sounds a good idea to check it indeed!

I'll push it with some rewording on the commit message.

In theory all the exit causes should have a proper value...