Don't add a connect callback if a function wasn't provided
Don't add a connect callback if a function wasn't provided

The new org.bluez.Audio code in device.c will request a connection without any
callback which'll cause a NULL pointer dereference if A2DP gets connected
before HFP/HSP. This patch fixes it.

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