gsm_04_08: Fix nullpointer deref

The pointers conn, conn->vsub and conn->vsub->last_tuple are checked,
but before the check those pointers are already dereferenced during
assignment. This defeats the purpose of the check. Lets dereference
those pointers after the check.

Fixes: CID#190404
Change-Id: Ice4992606f3799eac13154ec0b9f53e46d2e178e
1 file changed