Fixed setting state on adding or removing listeners. In the old setup,
the mask was only set in case *listeners.size() > 2. Otherwise, the mask
was always reset. Now, the reset is only performed if the number of
listeners drops to 0, and set if there is one listener present (assuming
it's the first).
Fixed allowing the video stream to continue when sending sticky
commands. In case a sticky commands is present, the commands are sent to
the drone too quickly. In result, the video stream halts (probably due
to CPU overload on the drone). By sleeping for a bit (10 ms for now,
this is just a guessed value, should be < the timeout off course) we
allow the video stream a large enough gap to get the data through
Merge branch 'fix-nav-listener'