Use the method grid.reset.

static/plugin_dbui/src/pgridexpertmenu.js

@@ -43,21 +43,11 @@ App.grid.ExpertMenu = Ext.extend(Object, {
     },
     
     /**
-     * Handler to reset filter and to reload the underlying data store
+     * Handler to reset grid, its filters and its paging options
      */    
     onReset: function () {
-
-        var grid = this,
-            store = this.getStore();
-
-        // remove gridFilter conditions        
-        delete store.baseParams.where;
-        
-        // send the clear signal in order to reset gridFilter
-        store.fireEvent('clear');
-        
-        // load the store with fresh data
-        store.load();
+        var grid = this;
+        grid.reset();
     }
 });