fix(selection): reset selectedCount on clearSelectedRows

If your data  is completely replaced by another array, then you need to call clearSelectedRows and it wasn't resetting the selectionCount

Author: swalters

src/features/selection/js/selection.js

@@ -554,6 +554,7 @@
           });
           service.decideRaiseSelectionBatchEvent( grid, changedRows, evt );
           grid.selection.selectAll = false;
+          grid.selection.selectedCount = 0;
         },
 
         /**