Typing into selected table throws an error

[Comandeer]

Are you reporting a feature request or a bug?

Bug

Provide detailed reproduction steps (if any)

1. Open https://sdk.ckeditor.com/samples/table.html
2. Select whole table using elements path.
3. Type any letter.

Expected result

Table is replaced with typed text.

Actual result

Table is replaced with typed text, but at the same moment error is thrown:

Uncaught TypeError: Cannot read property 'type' of null

Other details

• CKEditor version: 4.7.0+
• Installed CKEditor plugins: tableselection

[Comandeer]

It seems that the proposed fix introduced new issue:

1. Open CKEditor sample.
2. Open browser's console.
3. Clear the editor's content.
4. Insert table with nested table.
5. Select outer table.
6. Blur the editor.
7. Refocus the editor, but doesn't change the selection.
8. Press Delete.

Expected result:

Table is removed.

Actual result:

Table is removed, but there are warnings in the console:

[CKEDITOR] Error code: range-startcontainer.

Error code: range-endcontainer.

[mlewand]

The reason for above is #873, still I'll extract this issue to #874 so that we can track its progress.