SHACL validation: NullPointerException when shapes with sh:alternativePath importing <http://datashapes.org/dash>

How to replicate

Run

{{Graph shapesGraph = ModelFactory.createOntologyModel(OntModelSpec.OWL_DL_MEM).read("shapes.ttl", "TTL").getGraph();}}
Graph dataGraph = ModelFactory.createOntologyModel(OntModelSpec.OWL_DL_MEM).read("data.ttl", "TTL").getGraph();}}
validator = ShaclValidator.get();
return validator.validate(shapesGraph, dataGraph);

Files attached.

What is happening

The exception happens when a property shape with sh:alternativePath is evaluated inside ConstraintComponentSPARQL. I'm not sure why however it only happens when dash/tosh shapes are imported by a shape.

The exception seems to happen on line 239 of SparqlValidation.java:

RDFNode z = ModelUtils.convertGraphNodeToRDFNode(ShaclPaths.pathNode(path), model);

where pathNode() returns null - only supporting P_Link, not P_Alt and convertGraphNodeToRDFNode() then runs unchecked node.isVariable().

Stack trace:

parameterMapToPreBinding:239, SparqlValidation (org.apache.jena.shacl.engine.constraint)
validateMap:122, SparqlValidation (org.apache.jena.shacl.engine.constraint)
validate:87, SparqlValidation (org.apache.jena.shacl.engine.constraint)
lambda$validatePropertyShape$0:69, ConstraintComponentSPARQL (org.apache.jena.shacl.engine.constraint)
accept:-1, 1035363280 (org.apache.jena.shacl.engine.constraint.ConstraintComponentSPARQL$$Lambda$125)
forEach:75, Iterable (java.lang)
validatePropertyShape:68, ConstraintComponentSPARQL (org.apache.jena.shacl.engine.constraint)
evalConstraint:264, ValidationProc (org.apache.jena.shacl.validation)
validationPropertyShape:248, ValidationProc (org.apache.jena.shacl.validation)
validationPropertyShapes:228, ValidationProc (org.apache.jena.shacl.validation)
validateShape:219, ValidationProc (org.apache.jena.shacl.validation)
simpleValidationInternal:178, ValidationProc (org.apache.jena.shacl.validation)
simpleValidation:122, ValidationProc (org.apache.jena.shacl.validation)
simpleValidation:109, ValidationProc (org.apache.jena.shacl.validation)
simpleValidation:101, ValidationProc (org.apache.jena.shacl.validation)
validate:79, ShaclSimpleValidator (org.apache.jena.shacl.validation)
validate:91, ShaclSimpleValidator (org.apache.jena.shacl.validation)
validate:23, mytest (com.msd.gin.mrlitdi.test)
run:17, mytest (com.msd.gin.mrlitdi.test)
invoke0:-1, NativeMethodAccessorImpl (sun.reflect)
invoke:62, NativeMethodAccessorImpl (sun.reflect)
invoke:43, DelegatingMethodAccessorImpl (sun.reflect)
invoke:498, Method (java.lang.reflect)
runReflectiveCall:50, FrameworkMethod$1 (org.junit.runners.model)
run:12, ReflectiveCallable (org.junit.internal.runners.model)
invokeExplosively:47, FrameworkMethod (org.junit.runners.model)
evaluate:17, InvokeMethod (org.junit.internal.runners.statements)
runLeaf:325, ParentRunner (org.junit.runners)
runChild:78, BlockJUnit4ClassRunner (org.junit.runners)
runChild:57, BlockJUnit4ClassRunner (org.junit.runners)
run:290, ParentRunner$3 (org.junit.runners)
schedule:71, ParentRunner$1 (org.junit.runners)
runChildren:288, ParentRunner (org.junit.runners)
access$000:58, ParentRunner (org.junit.runners)
evaluate:268, ParentRunner$2 (org.junit.runners)
run:363, ParentRunner (org.junit.runners)
run:137, JUnitCore (org.junit.runner)
startRunnerWithArgs:69, JUnit4IdeaTestRunner (com.intellij.junit4)
startRunnerWithArgs:33, IdeaTestRunner$Repeater (com.intellij.rt.junit)
prepareStreamsAndStart:220, JUnitStarter (com.intellij.rt.junit)
main:53, JUnitStarter (com.intellij.rt.junit)