mail plugins errors

[eudm]

error "Cannot read property 'init' of null" in PluginManager.js on line 58

solution:
views Packt.view.mail.MailList and Packt.view.mail.MailMenu
must explicitly require
Ext.grid.plugin.DragDrop
and
Ext.tree.plugin.TreeViewDragDrop
referenced in the viewConfig.plugins configuration