attrib: Fix interactive gatttool segfault
attrib: Fix interactive gatttool segfault

Passing the special character single quote:

$gatttool -I
[   ][                 ][LE]> '
Segmentation fault (core dumped)

Checking g_shell_parse_argv fail status (return FALSE on failure), works
fine.

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