added null option to device query
added null option to device query

Qbitus/meshblu,osokay/IotServerCore,Qbitus/meshblu,masato/meshblu,jaambee/meshblu,octoblu/meshblu,ChemTics/meshblu,jaambee/meshblu,ChemTics/meshblu,atyenoria/meshblu,osokay/IotServerCore,octoblu/meshblu,ChemTics/meshblu,atyenoria/meshblu,masato/meshblu-dev,dommert/meshblu,masato/meshblu,dommert/meshblu,masato/meshblu-dev,atyenoria/meshblu,masato/meshblu,jaambee/meshblu,masato/meshblu-dev,dommert/meshblu,osokay/IotServerCore,Qbitus/meshblu