IE7, IE6 - Selection problem when destroying editor in ENTER_BR

[Jakub Ś]

This issue was reported in our supprot channel (Topic: Excluding auto generated paragraph (<p>) tags from CKeditor)

1. Insert in your config.js

   config.enterMode = CKEDITOR.ENTER_BR;	
   config.shiftEnterMode = CKEDITOR.ENTER_P;
   

2. Open AJAX sample
3. Type "This is some sample text"
4. Select E.g. "This i[s some sample text"
5. Remove editor, Create editor, Remove editor

Result: JS erro is thrown
Message: editor.getselection() is null or not an object
Line: 806
URI: /ckeditor/_source/plugins/wysiwygarea/plugin.js

Issue has been reproducible in IE6 and IE7 from CKEditor 3.5.3