PHP/MYSQL if else

I am creating a baseball website and I am learning php as I go. I have hit a snag with something I am trying to do; here is what my current code shows: MLB Scoreboard

here is my code: CODE

When I load my files that update the scores, if the game hasn't started the scores are NULL. Is there a code to change it to 0 without having to change it in my database. Any info will be helpful