geofence: disable altitude check if not configured
geofence: disable altitude check if not configured

It currently cannot be configured via mavlink mission protocol.

krbeverx/Firmware,Aerotenna/Firmware,dagar/Firmware,acfloria/Firmware,jlecoeur/Firmware,dagar/Firmware,Aerotenna/Firmware,acfloria/Firmware,jlecoeur/Firmware,PX4/Firmware,PX4/Firmware,dagar/Firmware,mje-nz/PX4-Firmware,krbeverx/Firmware,acfloria/Firmware,mje-nz/PX4-Firmware,mje-nz/PX4-Firmware,mcgill-robotics/Firmware,mje-nz/PX4-Firmware,mje-nz/PX4-Firmware,krbeverx/Firmware,acfloria/Firmware,acfloria/Firmware,mje-nz/PX4-Firmware,PX4/Firmware,mcgill-robotics/Firmware,PX4/Firmware,jlecoeur/Firmware,PX4/Firmware,jlecoeur/Firmware,krbeverx/Firmware,Aerotenna/Firmware,krbeverx/Firmware,PX4/Firmware,Aerotenna/Firmware,dagar/Firmware,mje-nz/PX4-Firmware,jlecoeur/Firmware,mcgill-robotics/Firmware,Aerotenna/Firmware,mcgill-robotics/Firmware,jlecoeur/Firmware,acfloria/Firmware,Aerotenna/Firmware,dagar/Firmware,acfloria/Firmware,krbeverx/Firmware,krbeverx/Firmware,mcgill-robotics/Firmware,mcgill-robotics/Firmware,Aerotenna/Firmware,PX4/Firmware,jlecoeur/Firmware,dagar/Firmware,jlecoeur/Firmware,dagar/Firmware,mcgill-robotics/Firmware