FlightTask initialize _dist_to_bottom
FlightTask initialize _dist_to_bottom

 - fixes Coverity CID 306248

krbeverx/Firmware,PX4/Firmware,mje-nz/PX4-Firmware,PX4/Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,PX4/Firmware,Aerotenna/Firmware,dagar/Firmware,PX4/Firmware,krbeverx/Firmware,acfloria/Firmware,Aerotenna/Firmware,dagar/Firmware,mje-nz/PX4-Firmware,krbeverx/Firmware,krbeverx/Firmware,dagar/Firmware,acfloria/Firmware,Aerotenna/Firmware,acfloria/Firmware,PX4/Firmware,Aerotenna/Firmware,mje-nz/PX4-Firmware,acfloria/Firmware,mje-nz/PX4-Firmware,PX4/Firmware,PX4/Firmware,mje-nz/PX4-Firmware,dagar/Firmware,krbeverx/Firmware,acfloria/Firmware,Aerotenna/Firmware,mje-nz/PX4-Firmware,krbeverx/Firmware,dagar/Firmware,acfloria/Firmware,dagar/Firmware,acfloria/Firmware,Aerotenna/Firmware,Aerotenna/Firmware,dagar/Firmware