HDHomeRun Scan Erroneous Channels

Whether scanning OTA (ATSC) or Cable (QAM) it seems to want to include some apparently erroneous channels that are just numbered. They show up in the web interface as "-", "- 2", "- 3", etc. Unsure how these are being produced. Trying to preview one shows a signal strength but no video. the associated mpgbuf for the tuner shows a zero size. This compared to a valid channel that shows a preview video and the associated mpgbuf file size is greater than zero.

Start by tracing the OTA and QAM scan handling that creates channel entries in the web interface, then compare the zero-size mpgbuf for a '-' channel with the mpgbuf for a valid channel. Done means erroneous numbered channels are no longer included, or their cause and expected handling are established, while valid previews continue to work.

Written by the indexing model from the issue text.