dix: fix broken XI event delivery during grabs.

If an implicit passive grab is active, the XI event mask is in
grab->deviceMask. Otherwise, for explicit grabs, the XI event mask is in
grab->eventMask.

Reported-by: Thomas Jaeger
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

dix/events.c

@@ -3863,6 +3863,9 @@ DeliverGrabbedEvent(InternalEvent *event, DeviceIntPtr thisDev,
             if (grabinfo->fromPassiveGrab  &&
                     grabinfo->implicitGrab)
                 mask = grab->deviceMask;
+            else
+                mask = grab->eventMask;
+
             FixUpEventFromWindow(thisDev, xi, grab->window,
                     None, TRUE);