obexd/MAP: Fix assigning pointer not value to 0
obexd/MAP: Fix assigning pointer not value to 0

The fix introduced by 455fb131f08cddc9759c877e38ebff3b4bd975b2 would
leave err value uninitialized and set the pointer to 0 which doesn't
make any sense.

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