Using tab key in a line with tabstops causes the cursor to move

[appreciated]

To reproduce:

1. Go to the demo page
2. Use the example "Basic Rich Text Editor with Tab-stops"
3. Remove the indentation in the first line
4. Begin readding the indentation by using the tab key

Expected behavior:

The cursor should not move if the tab key is pressed.

Actual behavior:

(After the second Tab) The cursor moves by one to the right if the tab key is pressed.