dvbtee-parser: check for a buffer before passing it to Parser.push
dvbtee-parser: check for a buffer before passing it to Parser.push

Signed-off-by: Michael Ira Krufky <00524723a60798c74a43fcc620c25dd7b9ece078@linuxtv.org>

mkrufky/node-dvbtee,mkrufky/node-dvbtee,mkrufky/node-dvbtee,mkrufky/node-dvbtee