profiles/gap: Handle error or no device name
profiles/gap: Handle error or no device name

Fixes segmentation fault when reading value of device name
characteristic returns error or no data.

pstglia/external-bluetooth-bluez,mapfau/bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,pkarasev3/bluez,ComputeCycles/bluez,pstglia/external-bluetooth-bluez,mapfau/bluez,silent-snowman/bluez,ComputeCycles/bluez,ComputeCycles/bluez,pkarasev3/bluez,pstglia/external-bluetooth-bluez,pkarasev3/bluez,mapfau/bluez,ComputeCycles/bluez,silent-snowman/bluez,silent-snowman/bluez,pkarasev3/bluez,silent-snowman/bluez