The class Action specifies its "parameters" member can be null (one calling getParameters() can get null).
The SaxUIHelper class does not check if the return value is null before using it (rev. 2, line 124), which can lead to a NullPointerException.

Easy workaround : just create the Action with an empty map as parameters.

Resolution : either do not permit null as 'parameters' member, or modify the SaxUIHelper class (and maybe some others) which don't check if null is returned.