RadDocument instance leaks through StylesGallery when RadDocument is set multiple times in a sequence to RadRichTextBox - for example by setting RadRichTextBox.Document property multiple times.

Steps to reproduce:

- Start application containing RadRichTextBox with StylesGallery

- Execute this code on a button click: 

            this.radRichTextBox.Document = new RadDocument();
            this.radRichTextBox.Document = new RadDocument();


Observed: RadDocument leaks through the styles gallery.


Available in LIB version: 2017.1.227