Fix bottom when deserializing XRRNotifyEvent in getEvent

This would crash any program that does

    xrrSelectInput dpy root rrCrtcChangeNotifyMask

and later calls getEvent on the received event.

CHANGES.md

@@ -3,6 +3,7 @@
 ## unknown
 
   * Fixed type of `xrrUpdateConfiguration`
+  * Fixed bottom when deserializing XRRNotifyEvent in `getEvent`
 
 ## 1.9.2 (2020-08-25)
 

Graphics/X11/Xlib/Extras.hsc

@@ -768,7 +768,7 @@ getEvent p = do
             type_ == rrEventBase + rrNotify -> do
             window   <- #{peek XRRNotifyEvent, window  } p
             subtype  <- #{peek XRRNotifyEvent, subtype } p
-            let subtype_ = fromIntegral subtype_
+            let subtype_ = fromIntegral subtype
             case () of
                 _ | subtype_ == rrNotifyCrtcChange -> do
                     crtc           <- #{peek XRRCrtcChangeNotifyEvent, crtc     } p