added CheckContainer to avoid crashing when checks fail with an exception

CityDoctorParent/CityDoctorValidation/src/main/java/de/hft/stuttgart/citydoctor2/check/Checker.java

@@ -55,6 +55,7 @@ import de.hft.stuttgart.citydoctor2.check.error.AttributeMissingError;
 import de.hft.stuttgart.citydoctor2.check.error.AttributeValueWrongError;
 import de.hft.stuttgart.citydoctor2.check.error.SchematronError;
 import de.hft.stuttgart.citydoctor2.checkresult.utility.CheckReportWriteException;
+import de.hft.stuttgart.citydoctor2.checks.CheckContainer;
 import de.hft.stuttgart.citydoctor2.checks.CheckPrototype;
 import de.hft.stuttgart.citydoctor2.checks.Checks;
 import de.hft.stuttgart.citydoctor2.checks.SvrlContentHandler;
@@ -685,7 +686,7 @@ public class Checker {
 				boolean hasUnusedDependency = searchForUnusedDependency(usedChecks, c);
 				if (!hasUnusedDependency) {
 					iterator.remove();
-					layer.add(c);
+					layer.add(new CheckContainer(c));
 				}
 			}
 			if (layer.isEmpty()) {