Coverity fix in driver/xen.c

CID 703184 (#1 of 1): Dereference before null check (REVERSE_INULL)check_after_deref: Null-checking name suggests that it may be null, but it has already been dereferenced on all paths leading to the check.
Merge pull request #204 from tklengyel/coverity_fixes6

Coverity fix in driver/xen.c