Merge branch 'js/packet-read-line-check-null'

Merge branch 'js/packet-read-line-check-null'

Some low level protocol codepath could crash when they get an
unexpected flush packet, which is now fixed.

* js/packet-read-line-check-null:
  always check for NULL return from packet_read_line()
  correct error messages for NULL packet_read_line()