Fixed hardfault on fast proc
Fixed hardfault on fast proc

_baro_topic can be null in init sequence
   init call collect before the topic is inited.

I think this pattern is repeated in other drivers. I would suggest
allowing null in orb_publish to just return.

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