Excludes can raise a NPE if value is empty in POM file

JBehave Maven goals support the property "excludes".

See: http://jbehave.org/reference/stable/maven-goals.html

If "excludes" is used in the POM file and if it is empty, then a NPE occurs in AbstractScanner.java:327

This class is called from: org.jbehave.core.io.StoryFinder.scan(StoryFinder.java:183)

JBehave could be easier to configure concerning "excludes" if this would allow empty value. That would mean, that nothing is excluded if the value is empty. No need to cause a NPE because of this.

I did not verify it, but I think a NPE is also raised when "includes" are empty. It would be better if no NPE is thrown. If the value is empty it can be interpreted as nothing is included or everything is included, whatever makes sense to you as a default.