virtio-devices: Test notifier with OOB vector returns None

Verify that requesting a notifier with an out-of-bounds MSI-X
vector returns None instead of panicking.

Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>

virtio-devices/src/transport/pci_device.rs

@@ -1391,4 +1391,11 @@ mod unit_tests {
         let intr = make_msix_interrupt(2);
         intr.trigger(VirtioInterruptType::Queue(0)).unwrap();
     }
+
+    #[test]
+    fn notifier_with_oob_vector_returns_none() {
+        let intr = make_msix_interrupt(2);
+        intr.queues_vectors.lock().unwrap()[0] = 0xFFFE;
+        assert!(intr.notifier(VirtioInterruptType::Queue(0)).is_none());
+    }
 }