Fix universe inset being too large on two sides

Author: a11ce

htdp-lib/2htdp/private/world.rkt

@@ -258,8 +258,8 @@
                (style '(no-hscroll no-vscroll))
                (horizontal-inset INSET)
                (vertical-inset INSET)))
-        (send editor-canvas min-client-width (+ width INSET INSET))
-        (send editor-canvas min-client-height (+ height INSET INSET))
+        (send editor-canvas min-client-width (sub1 (+ width INSET INSET)))
+        (send editor-canvas min-client-height (sub1 (+ height INSET INSET)))
         (set!-values (enable-images-button disable-images-button)
                      (inner (values void void) create-frame/universe frame play-back:cust))
         (send editor-canvas focus)