qemu: Fix segfault in qemuDomainPrimeVirtioDeviceAddresses
qemu: Fix segfault in qemuDomainPrimeVirtioDeviceAddresses

On aarch64, lauch vm with the follow configuration:

<interface type="hostdev" managed="yes">
  <mac address="fa:16:3e:14:41:00"/>
  <source>
    <address type="pci" domain="0x0000" bus="0x01" slot="0x0b" function="0x2"/>
  </source>
</interface>

libvirtd will crash when accessing net->model.

Signed-off-by: Wang Yechao <d156c2278b59b97b85e8218b42611783bb8435e2@zte.com.cn>
Reviewed-by: Andrea Bolognani <3ada0bee826c753786fdbba72243dfba997094cf@redhat.com>

jardasgit/libvirt,olafhering/libvirt,jardasgit/libvirt,olafhering/libvirt,nertpinx/libvirt,olafhering/libvirt,zippy2/libvirt,nertpinx/libvirt,jfehlig/libvirt,jardasgit/libvirt,andreabolognani/libvirt,crobinso/libvirt,crobinso/libvirt,libvirt/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,eskultety/libvirt,jfehlig/libvirt,andreabolognani/libvirt,nertpinx/libvirt,jardasgit/libvirt,eskultety/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,libvirt/libvirt,nertpinx/libvirt,eskultety/libvirt,libvirt/libvirt,olafhering/libvirt,zippy2/libvirt,zippy2/libvirt,fabianfreyer/libvirt,crobinso/libvirt,zippy2/libvirt,jfehlig/libvirt,jfehlig/libvirt,eskultety/libvirt,libvirt/libvirt,jardasgit/libvirt,crobinso/libvirt,eskultety/libvirt