Fix an NPE in the repair service

Signed-off-by: Alexander Diewald <diewald@fortiss.org>

org.fortiss.af3.exploration.alg/src/org/fortiss/af3/exploration/alg/service/internal/.ratings

 ExpSpecTransformationService.java d791fcf0a4f6b2b09059edd4cbe2499f5b49b114 YELLOW
 ExplorationEvaluationService.java b0b6d1ac1d20bc3dea0cb1212af623adcca712c6 RED
 ExplorationFeatureService.java 9bdc850105efb7a8e499d3aa87536f9b026e5b4d YELLOW
-ExplorationRepairService.java e7251a6ac6f59b171469758ed7a59f2314e31482 RED
+ExplorationRepairService.java d6a83dcd2d15c6b5ae5771bb9bdd2410043e141f RED
 ExplorationTransformationService.java 0731c5e22ce754bc4d14c4cf8aeadcd6845dc78f RED

org.fortiss.af3.exploration.alg/src/org/fortiss/af3/exploration/alg/service/internal/ExplorationRepairService.java

@@ -15,6 +15,8 @@
 +--------------------------------------------------------------------------*/
 package org.fortiss.af3.exploration.alg.service.internal;
 
+import static java.util.Collections.emptyList;
+
 import java.lang.reflect.Constructor;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -102,7 +104,11 @@ public class ExplorationRepairService extends ObjectAwareServiceBase<IRepairModu
 			throws ExplorationException {
 		List<IRepairModule<T>> repairModuleInstances = new ArrayList<>();
 		Collection<IRepairModule<?>> registeredHandlers =
-				(Collection<IRepairModule<?>>)(Collection<?>)(getRegisteredHandlers(genotype.getClass()));
+				(Collection<IRepairModule<?>>)(Collection<?>)(getRegisteredHandlers(
+						genotype.getClass()));
+		if(registeredHandlers == null) {
+			return emptyList();
+		}
 
 		for(IRepairModule<?> curModuleTemplate : registeredHandlers) {
 			IRepairModule<T> moduleInstance;