commit 0e0e339a816f221cf0325393b16ed5dc6f180616
Author: Hubert Figuiere <hub@figuiere.net>
Date:   Mon Jun 1 16:02:32 2009 -0400

    Fix a crash in Xephyr. bug #22024

diff --git a/dix/events.c b/dix/events.c
index ee6ac9e..356cbf3 100644
--- a/dix/events.c
+++ b/dix/events.c
@@ -2122,8 +2122,11 @@ DeliverEventsToWindow(DeviceIntPtr pDev, WindowPtr pWin, xEvent
                 tempGrab.genericMasks->next = NULL;
             }
         }
-	(*pDev->deviceGrab.ActivateGrab)(pDev, &tempGrab,
+        if(*pDev->deviceGrab.ActivateGrab)
+        {
+          (*pDev->deviceGrab.ActivateGrab)(pDev, &tempGrab,
                                         currentTime, TRUE | ImplicitGrabMask);
+        }
     }
     else if ((type == MotionNotify) && deliveries)
 	pDev->valuator->motionHintWindow = pWin;