Copter: landing detector internal error in Guided mode using set_attitude_target

[rmackay9]

How to reproduced the problem:

• start copter in SITL
• param set DISARM_DELAY 0 (to disable automatic disarming while landed)
• param set GUID_OPTIONS 8 (SetAttitudeTarget interprets Thrust As Thrust)
• GUIDED (to switch the vehicle to Guided mode)
• arm throttle
• attitude 1 0 0 0 0.5 (see developer SET_ATTITUDE_TARGET instructions here)

"Internal Error 0x100000" should appear on the GCS's messages tab as shown below

The code that triggers this error is here in land_detector.cpp. Another related line in mode_guided.cpp is here.

There is a similar issue for Stabilize mode documented here.