Comment 2 for bug 761831

StacktraceTop:
 __kernel_vsyscall ()
 raise (sig=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
 abort () at abort.c:92
 g_assertion_message (domain=0x0, file=0x80a5fa6 "brasero-drive-settings.c", line=83, func=0x80a5fc0 "brasero_drive_settings_get_mapping_speed", message=<value optimized out>) at /build/buildd/glib2.0-2.28.5/./glib/gtestutils.c:1358
 g_assertion_message_expr (domain=0x0, file=0x80a5fa6 "brasero-drive-settings.c", line=83, func=0x80a5fc0 "brasero_drive_settings_get_mapping_speed", expr=0x80a5f97 "medium != NULL") at /build/buildd/glib2.0-2.28.5/./glib/gtestutils.c:1369