PreviewPane: remove redundant null check

Noticed by Findbugs.
Merge pull request #648 from melissalinkert/findbugs-fix

Java 1.7/Findbugs fixes
Setting schema to 2013-10 for inprogress files
Introduce Configuration objects, see #3673
Adding stub transforms and sample files
Get XMLMockObjects to compile
Changes to xsd-fu for new schema
Adding ConfigurationSettings to Plane
Adding wide range of datetime annotations
Adding date-time extreme sample
Add map base types and MapAnnotation, see #11341
Add GenericSource using the Map type, see #11344
Adding plural markers to map