obexd: Return Bad Request when search value is empty on PullvCardListing
obexd: Return Bad Request when search value is empty on PullvCardListing

No matter the search attribute, search value can't be an empty
string. OBEX error bad request is returned for this scenario.

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