fix const

src/main/java/kieker/analysis/dev/nestedgraph/NestedGraph.java

@@ -25,7 +25,7 @@ public class NestedGraph<T extends Graph> implements Graph, WrapperGraph<T> {
 	private final Set<NestedGraphPartition> partitions = new HashSet<>();
 
 	public NestedGraph(final T baseGraph) {
-		this.baseGraph = new PartitionGraph<>(baseGraph, PARTITION_KEY, "");
+		this.baseGraph = new PartitionGraph<>(baseGraph, PARTITION_KEY, DEFAULT_PARTITION);
 		this.features = this.baseGraph.getFeatures().copyFeatures();
 		this.features.isWrapper = true;
 	}