Statistics: handle correctly page change when reading paused

As currently we only handle ReadingPaused/Resumed on suspend
and resume, no page change should happen while paused, so
there is no current issue to fix. But let's get ready for
other use cases (which may be brought in by user patches,
ie. pausing while the SkimWidget is displayed, and obviously
triggers page changes).

plugins/statistics.koplugin/main.lua

@@ -2622,6 +2622,13 @@ function ReaderStatistics:onPageUpdate(pageno)
         return
     end
 
+    if self._reading_paused_ts then
+        -- Reading paused: don't update stats, but remember the current
+        -- page for when reading resumed.
+        self._reading_paused_curr_page = pageno
+        return
+    end
+
     -- We only care about *actual* page turns ;)
     if self.curr_page == pageno then
         return
@@ -2773,6 +2780,11 @@ function ReaderStatistics:onReadingResumed()
             if data_tuple then
                 data_tuple[1] = data_tuple[1] + pause_duration
             end
+            if self._reading_paused_curr_page and self._reading_paused_curr_page ~= self.curr_page then
+                self._reading_paused_ts = nil
+                self:onPageUpdate(self._reading_paused_curr_page)
+                self._reading_paused_curr_page = nil
+            end
         end
     end
     self._reading_paused_ts = nil