Structural Connection Validity issue source definition seems broken
The definition at https://gitlab.simantics.org/simantics/platform/-/blob/master/bundles/org.simantics.structural.ontology/graph/Structural.pgraph#L321-327 seems faulty as the constraint it defines does not have any validator relation defined which causes crashes at https://gitlab.simantics.org/simantics/platform/-/blob/master/bundles/org.simantics.issues.common/src/org/simantics/issues/common/DependencyIssueValidator2.java#L63.
When issue tracking is started, https://gitlab.simantics.org/simantics/platform/-/blob/master/bundles/org.simantics.issues.common/src/org/simantics/issues/common/ActiveProjectIssueSources.java will find STR.ConnectionValidationConstraint.Source
as well as all other sources and if the user happens to use the Select Available Issue Sources dialog to enable Structural connection validity, crashes will start occurring all the time.