Repro for a potential bug in qunit v2.17.0

To reproduce:

1. Open test.html in a browser
2. Filter for something that doesn't exist in the tests, such as 'cat'
3. See no exception thrown and curious results

To see node behavior:

1. npm install
2. npx qunit --filter='cat'
3. Observe error as expected

To see v2.16.0 behavior

1. Open test-2-16.html in a browser
2. Filter for something that doesn't exist in the tests, such as 'cat'
3. See exception thrown in console, though unfortunate lack of feedback in UI