] Assume that you have created a JButton with the name "b1", a JTextField with the name "f1", and a JTextField with the name "a1". When the button is clicked, you need to take the number written in f1, and the number in a1, then add the two numbers, and put the result back in f1. Consider an empty string or a space as the number 0.

1. Write the code for this button handler.

2. Protect your code against any possible crashing.