Ext4 Grid: instead of unbinding store set an empty store
Ext4 Grid: instead of unbinding store set an empty store

this is also what ext does if grid is created without store.
This fixes problem related with this error:
http://www.sencha.com/forum/showthread.php?178869-var-store-this.up(-store-).store-Error

Ben-Ho/densajs,koala-framework/densajs