Malformed Cucumber scenario Examples causes NullPointerException on Execution Page

The following cucumber scenario examples causes a nullPointerException to be displayed on test execution page:

Given I have entered <input_1> into the calculator
And I have entered <input_2> into the calculator
When I press <button>
Then the result should be <output> on the screen
Examples:
input_1 input_2 button output
20 30 add 50
2 5 add 7
0 40 add 40
4 50 add 54