Delete columns when rows are splitted

[Robert]

• Insert table (3x3)
• Split left-middle cell horizontally
• Try to delete last column

Column is being removed but console error occurs.

Uncaught TypeError: Cannot read property 'ownerDocument' of undefined

[Jakub Ś]

Problem can be reproduced from CKEditor 3.5.1 rev. [6328] in every browser.

Please note that fix for this revision was made in #7811.