fixed nullpointer exception for filepaths without parent folder

converter/src/main/java/lcsb/mapviewer/converter/Converter.java

@@ -83,7 +83,10 @@ public abstract class Converter {
 			throws InconsistentModelException, IOException, ConverterException {
 		String xml = model2Xml(model);
 		File file = new File(filePath);
-		file.getParentFile().mkdirs();
+    File parentFile = file.getParentFile();
+    if (parentFile != null) {
+      parentFile.mkdirs();
+    }
 		try (PrintWriter out = new PrintWriter(file)) {
 			out.println(xml);
 		}