If a document with default tab stops width 0 or imported or the value is set from the UI, measuring the document when it contains a tab causes an InvalidOperationException with message "MeasureOverride returned Nan".

Workaround: If the case is importing a document, change the default tab stop width to value which is not 0.

            if (document.DefaultTabWidth == 0)
            {
                  // set this to large number if there are performance problems, e.g. 0.5. 
                  document.DefaultTabWidth = 0.01;
            }

Steps to reproduce:
1. Load RadRichTextBox and add text in it.
2. Change default tab stops value from the Paragraph Properties Dialog -> Tabs Dialog to 0''
3. Add a tab to the paragraph.
Observed: InvalidOperationException with message "MeasureOverride returned NaN" is thrown.

Fix available in LIB Version 2017.3.1120.