Styles removed when cursor is placed at the beginning of a new line

[Joel Mizzoni]

Reproduced on demo and nightly build on IE11 on Windows 8.1

Steps to reproduce:

1. Apply some font styling (font family, size, colour).
2. Type a line and create a new line by pressing enter
3. Click the beginning of the new line to position the cursor there. (Optionally, reposition the cursor elsewhere first).
4. Begin typing again

Behaviour:

Expected: The text styling on the new line should be the same as that on the previous line

Actual: The style has reset to the editor's default

[Jakub Ś]

This issue is related to #12689.

We should remove empty inline elements in non-empty lines while we could leave empty inline elements in empty lines. This second case requires handling selection as well because when you go to new line an empty inline element is created. If you move cursor, you leave that element and there is no way to enter it again. This would have to be done my selection modification.