Fix cover browser breaking if you click on a book in the bok list while cover browser is animated

src/calibre/gui2/cover_flow.py

@@ -205,8 +205,8 @@ class CoverFlowMixin(object):
                     sm.select(index, sm.ClearAndSelect|sm.Rows)
                     self.library_view.setCurrentIndex(index)
         except:
-            pass
-
+            import traceback
+            traceback.print_exc()
 
     def sync_listview_to_cf(self, row):
         self.cf_last_updated_at = time.time()

src/calibre/gui2/pictureflow/pictureflow.cpp

@@ -496,6 +496,7 @@ int PictureFlowPrivate::currentSlide() const
 
 void PictureFlowPrivate::setCurrentSlide(int index)
 {
+  animateTimer.stop();
   step = 0;
   centerIndex = qBound(index, 0, slideImages->count()-1);
   target = centerIndex;