racket/gui: double-check size on attmpt to set editor scroll

A scroll request could fail if a resize notification is still
in flight (i.e., queued but not yet executed), so double-check
the size on a scroll request.

Closes PR 13582

collects/mred/private/wxme/editor-canvas.rkt

@@ -297,14 +297,17 @@
        (lambda ()
          (unless (and media
                       (send media get-printing))
-           (begin-refresh-sequence)
-           (let-boxes ([w 0]
-                       [h 0])
-               (get-size w h)
-             (unless (and (= w lastwidth)
-                          (= h lastheight))
-               (reset-size)))
-           (end-refresh-sequence))))))
+           (maybe-reset-size))))))
+
+  (define/private (maybe-reset-size)
+    (begin-refresh-sequence)
+    (let-boxes ([w 0]
+                [h 0])
+        (get-size w h)
+      (unless (and (= w lastwidth)
+                   (= h lastheight))
+        (reset-size)))
+    (end-refresh-sequence))
 
   (define/private (reset-size)
     (reset-visual #f)
@@ -934,6 +937,8 @@
     (let ([savenoloop? noloop?])
       (set! noloop? #t)
       
+      (maybe-reset-size)
+
       (when (and (x . > . -1)
                  (not fake-x-scroll?))
         (when (positive? scroll-width)