firmware: watchdog loop with configuration without sensors

[pat1]

disconnect all sensor from master board and get:

#Configuration received... [ OK ]
#Load configuration... [ OK ]
#--> type: report-gsm
#--> version: 3.2
#--> sensors: 6
#--> gsm apn: ibox.tim.it
#--> gsm username: 
#--> gsm password: 
#--> ntp server: it.pool.ntp.org
#--> mqtt server: test.rmap.cc
#--> mqtt port: 1883
#--> mqtt root topic: report/pat1/1165625,4485892/fixed/
#--> mqtt maint topic: maint/pat1/1165625,4485892/fixed/
#--> mqtt subscribe topic: report/pat1/1165625,4485892/fixed/rx
#--> mqtt username: pat
#--> mqtt password: password

#--> 1: I2C-ITH [ 0x23 ]: 254,0,0/103,2000,-,-/  [ FAIL ]
#Configuration received... [ OK ]
#Load configuration... [ OK ]
#--> type: report-gsm
#--> version: 3.2
#--> sensors: 6
#--> gsm apn: ibox.tim.it
#--> gsm username: 
#--> gsm password: 
#--> ntp server: it.pool.ntp.org
#--> mqtt server: test.rmap.cc
#--> mqtt port: 1883
#--> mqtt root topic: report/pat1/1165625,4485892/fixed/
#--> mqtt maint topic: maint/pat1/1165625,4485892/fixed/
#--> mqtt subscribe topic: report/pat1/1165625,4485892/fixed/rx
#--> mqtt username: pat
#--> mqtt password: password

#--> 1: I2C-ITH [ 0x23 ]: 254,0,0/103,2000,-,-/  [ FAIL ]
#Configuration received... [ OK ]
#Load configuration... [ OK ]
#--> type: report-gsm
#--> version: 3.2
#--> sensors: 6
#--> gsm apn: ibox.tim.it
#--> gsm username: 
#--> gsm password: 
#--> ntp server: it.pool.ntp.org
#--> mqtt server: test.rmap.cc
#--> mqtt port: 1883
#--> mqtt root topic: report/pat1/1165625,4485892/fixed/
#--> mqtt maint topic: maint/pat1/1165625,4485892/fixed/
#--> mqtt subscribe topic: report/pat1/1165625,4485892/fixed/rx
#--> mqtt username: pat
#--> mqtt password: password