Is parsing a string in the onTick method crashing my app?

Integer.parseInt can throw a NumberFormatException which would cause the application to stop abruptly if not caught.
This happens when the String that you're passing as parameter of parseInt isn't recognized as a decimal number.
The fact that this happens almost instantaneously in your code is due to the fact that the EditText.getText().toString() is just returning "", since the user has not typed any number in the widget.
What you can do is simply manage the exception with a try-catch statement:

int givenAnswer = 0; // initialize accordingly with your needs
try {
    givenAnswer = Integer.parseInt(userAnswer.getText().toString());
} catch (NumberFormatException e) {
    // return or do something else to deal with the problem
}

if(givenAnswer == actualIntAnswer){
    ...
}
...