TrackChange-INS moves SpellCheck-markup to wrong position

problem:

• Open a segment with content that will get marked as SpellCheck-error. Insert new content before the first error. The next SpellCheck will result in wrong positions of the errors behind the new INS.

solution:

• toString() on ranges keeps invisible characters (e.g. from the TrackChanges' INS-tags) => force TrackChanges to leave the Editor without the invisible INS-placeholders.