nullpointerexception in shaded JAR (for schematron)

[jstaerk]

I'd like to perform the actual validation against the ZUGFeRD
schematron, more precisely against the generated XSL file.

I included ph-schematron as dependency, which will throw me
noClassFound-Runtime exceptions if I only include it in the pom. I tried
to solve that by shading the apparently required classes into the JAR.
The issue is: if I do, I will inevitably run into a Nullpointerexception.

I left one comment in the pom.xml and two in
src/main/java/ZUV/ZUGFeRDExtractor.java in the current master [37794a4]
which, if removed, should perform the validation but previously run into
the NullPointerException at
org.verapdf.processor.FeaturesPluginsLoader.initializeExtractor(FeaturesPluginsLoader.java:132)
.

Can someone please help?