TauLabs/TauLabs — pull request #866 by peabody124 (2013-08-17 22:45:02+00:00)
Title: Transmitter Control: only set AltHoldDesired when exists

Because AltitudeHoldDesired is only initialized when the module
is running (which applies at startup) but the flight mode
position can be changed on the fly, this can allow the FC to
write to an object that doesn't exist and then crash.

Fixes #865