[bugfix] fix sub extention for filename throw indexout or range excetpion

atms-api/src/main/java/pwc/taxtech/atms/controller/OutputInvoiceController.java

@@ -150,8 +150,7 @@ public class OutputInvoiceController {
     }
 
     private String GetExtension(String file) {
-        return file.substring(file.lastIndexOf(".") + 1, file.length()
-                - file.lastIndexOf("."));
+        return file.substring(file.lastIndexOf(".") + 1, file.length());
     }
 
 }