[unrelated] Close execution graphml files
diff --git a/plugins/org.eclipse.qvtd.pivot.qvtimperative/src/org/eclipse/qvtd/pivot/qvtimperative/evaluation/Execution2GraphVisitor.java b/plugins/org.eclipse.qvtd.pivot.qvtimperative/src/org/eclipse/qvtd/pivot/qvtimperative/evaluation/Execution2GraphVisitor.java
index 440ecb9..22b0e98 100644
--- a/plugins/org.eclipse.qvtd.pivot.qvtimperative/src/org/eclipse/qvtd/pivot/qvtimperative/evaluation/Execution2GraphVisitor.java
+++ b/plugins/org.eclipse.qvtd.pivot.qvtimperative/src/org/eclipse/qvtd/pivot/qvtimperative/evaluation/Execution2GraphVisitor.java
@@ -137,7 +137,7 @@
 			GraphMLStringBuilder s = new GraphMLStringBuilder();
 			Execution2GraphVisitor execution2GraphVisitor = new Execution2GraphVisitor(s);
 			tx.accept(execution2GraphVisitor);
-			outputStream.write(s.toString().getBytes());
+			outputStream.write(s.close().getBytes());
 			outputStream.close();
 		} catch (IOException e) {
 			// TODO Auto-generated catch block