HDP: Set error message on error condition
HDP: Set error message on error condition

Fixes clang warning:
...
  CC       profiles/health/bluetoothd-hdp.o
profiles/health/hdp.c:1778:13: warning: Access to field 'message'
results in a dereference of a null pointer (loaded from variable 'gerr')
                                                "%s", gerr->message);
                                                      ^~~~~~~~~~~~~
...

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