fix frame registration on show' when current-eventspace' is weird

(i.e., not the frame's eventspace)
 Closes PR 11573

original commit: ffd4193e32317f730b9dd064aa00df2ebc1cb75b

collects/mred/private/wx/cocoa/window.rkt

@@ -122,8 +122,9 @@
        ;; Make sure we're in the right eventspace:
        (let ([wx (->wx wxb)])
          (and wx
-              (eq? (current-eventspace)
-                   (send wx get-eventspace))))
+              (eq? (current-thread)
+                   (eventspace-handler-thread
+                    (send wx get-eventspace)))))
        ;; Right event space, so handle the event:
        (do-mouse-event wxb event 'motion #f #f #f))]
   [-a _void (mouseEntered: [_id event]) 

collects/mred/private/wx/common/queue.rkt

@@ -453,9 +453,9 @@
     (queue-event es cb 'timer-remove)))
 
 (define (register-frame-shown f on?)
-  (queue-event (current-eventspace) f (if on?
-                                          'frame-add
-                                          'frame-remove)))
+  (queue-event (send f get-eventspace) f (if on?
+                                             'frame-add
+                                             'frame-remove)))
 
 (define (get-top-level-windows [e (current-eventspace)])
   ;; called in event-pump thread