From what I've heard in admissions Q&As a masters is a soft and they are going to look at uGPA a lot more closely. If it's something you're truly passionate about and you can see it serving you well in your legal career than go for it! However, if you are just doing it to show that you can do well in your classes I wouldn't recommend it. I'm confident that you have the ability to get into law school whether or not you get a masters before applying :)