Showing a score of zero out of zero isn't very professional. Let's add some logic so that the score is only displayed (a non-empty string) if the total number of attempts is greater than zero:
void Start(){
Text scoreText = GetComponent<Text>();
int totalAttempts = Player.scoreCorrect + Player.scoreIncorrect;
// default is empty string
string scoreMessage = "";
if( totalAttempts > 0){
scoreMessage = "Score = ";
scoreMessage += Player.scoreCorrect + " / " + totalAttempts;
}
scoreText.text = scoreMessage;
}