Add code check to avoid access violation.

Signed-off-by: ydong10
Reviewed-by: rsun3

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@13014 6f19259b-4bc3-4df7-8a09-765794883524

MdeModulePkg/Core/Dxe/Dispatcher/Dispatcher.c

@@ -544,6 +544,7 @@ CoreDispatcher (
           &DriverEntry->ImageHandle,
           sizeof (DriverEntry->ImageHandle)
           );
+        ASSERT (DriverEntry->ImageHandle != NULL);
   
         Status = CoreStartImage (DriverEntry->ImageHandle, NULL, NULL);