session.exportDocumentView() generates unparsable XML if a JCR Property contains invalid XML character

I came across this issue in AEM, where user content can contain all kinds of special characters. In my case it was a 0x3 character (^C) in a node property which was written in the JCR XML as-is, and it resulted in a unparsable output. 

IMO control characters, non-characters and out-of-unicode-range characters should be skipped when writing XML. These can come from user data and can act as a "poison pill" breaking the export/import functionality. 

The PR is coming.