Fix master backend crashing when receiving events from a slave

This is a workaround for 0.27 and requires a proper fix.

Fixes #11316

Signed-off-by: Daniel Kristjansson <danielk@cuymedia.net>
Signed-off-by: Stuart Morgan <smorgan@mythtv.org>
(cherry picked from commit a6c0330baa5ab01d3877a3d56818c3fcf8068a28)