Added null value check of userAgentString when parsing its value in the Browser and OperatingSystem objects. Updated associated unit tests to verify that UNKNOWN is returned for null userAgentString input. This fixes reported issue #46.
Merge pull request #47 from lewisdawson/trunk

Added null value check of userAgentString when parsing

Thank you. I wanted to pick the NPE issue up but am extremely busy with other things at the moment. Appreciating your help!