If your test is failing when nothing is wrong then make it top priority to fix it, or delete it. No test > not working test. These tests will make you no longer trust your test results and they will lose value. You need good dependable tests to be the support beams of your application.
When you delete a test that is not working you have to make sure that there is still some test that covers the code. You can do this with a code coverage tool or do what's called the Poor man's code coverage. Break the code and see what tests failed.