IE8 IE7: Copy, select, paste causes error

[Jakub Ś]

Issue has been reproducible in IE8 and IE7 from CKEditor 3.6.2 rev [7239]

To reproduce:

1. Open replace by code sample
2. Select word "some"
3. Press Copy toolbar button. When prompted to allow clipboard access click yes.
4. Select word "using"
5. Press toolbar button "Paste as plain text" or "Paste from word or "Paste". When prompted to allow clipboard access click yes

Result: JS error is thrown.
In IE8
Message: Invalid argument
Line: 241
URI: /3.6.2/ckeditor/_source/core/dom/node.js

In IE7
Message: Invalid argument
Line: 241
URI: /3.6.2/ckeditor/_source/plugins/selection/plugin.js

[Jakub Ś]

DUP of #8520