Insertion of unwanted   when you backspace and insert new text

[Eric Amodio]

When deleting text and inserting a space (I think it needs to be multiline so that there are p tags), if you switch to the source view you will see an   inserted for a single space between words that should not be there.

Steps to reproduce

To reproduce:

1. Use the sample on ​http://sdk.ckeditor.com/samples/uicolor.html
2. Put the cursor on the at the end of the was in the 2nd line
3. Press backspace twice to delete the as in was
4. Press the spacebar and then any letter (or word whatever)
5. Switch to the source view and observe that an   was inserted after the character (word) you inserted.

My uneducated guess is that this might happen because when you add that space there are 2 spaces next to each other, so the latter space gets turned into an   (which would be correct if you stopped there), but then when you press the next letter separating the 2 spaces, the   is persisted rather than changing back to a space

Expected result

A space should be inserted

Actual result

A   is inserted

Other details (browser, OS, CKEditor version, installed plugins)

CKEditor 4.6.2 (Standard) (revision 580bcaf)

Chrome: 57.0.2987.133

macOS: Sierra 10.12.4