Fix "Clear results" not releasing some memory

Author: nanawel

src/nnwl/jduplicatefinder/ui/ResultsTreeModel.java

@@ -241,6 +241,7 @@ public boolean deleteFileAndTreeNode(Path path, boolean recursive) {
 	public void resetResults() {
 		this.getRoot().removeAllChildren();
 		this.fileResultNodes.clear();
+		this.directoryNodes.clear();
 		this.totalNodesCount = 0;
 		logger.debug("Results have been reset");
 	}