FIx Game background music bug

[XUEHUANG521]

Description

Task: Fix bug that background music didn't play when enter into Main Game Screen
Feature: Team 5

Find out where does the bug came from and modify MainGameScreen.java to fix the bug

Dependencies

None.

Milestones

• Background Music played when enter into Main Game Screen.

Members

Xue Huang (@XUEHUANG521) (Xue huang)