title: TypeError: b is null extjs4
body: <p>My app has a grid, on double click on a record a window appear. In this windows there are two tabs, in the first I print a table with all the information of the selected row, in the second tab I have another grid linked with another store that display a sort of "logger" to see the activities of the selected row. My problem is that when I double click on a row the window appears and the activity store is loaded perfectly. But if I close the window and then I double click on another row, the Activity tab is empty and the error is <code>TypeError: b is null</code>.</p>
  
  <p>EDIT: Solved, I created the grid only one time, I have to create the grid everytime I create the window</p>