ReaderView: Recompute page layout when toggling ReaderFooter in

non-reflowable documents.

The code only handled setups with "reclaim bar height" enabled (because
that's my usual workflow, har har), but would have broken in various
more or less obvious ways without it, depending on the exact layout/zoom
settings.
The previous attempts at handling the no-reclaim case were focused
on scroll mode, which is a bit of a nightmare. This approach should
deal as well/badly as the previous one in scroll mode, but actually
handle page mode properly ;).

Re #9979

frontend/apps/reader/modules/readerfooter.lua

@@ -2199,8 +2199,8 @@ function ReaderFooter:_updateFooterText(force_repaint, force_recompute)
     if force_repaint then
         -- If there was a visibility change, notify ReaderView
         if self.visibility_change then
-            self.ui:handleEvent(Event:new("ReaderFooterVisibilityChange"))
             self.visibility_change = nil
+            self.ui:handleEvent(Event:new("ReaderFooterVisibilityChange"))
         end
 
         -- NOTE: Getting the dimensions of the widget is impossible without having drawn it first,