fix(ngMock): return immediately from mock $interval.cancel() when no promise argument is supplied

[dluxemburg]

This is a fix for a possible cause of issue #6099.

Calling $interval.cancel() without supplying the expected argument would cause a TypeError. There was a test for this but it was incomplete because it did not setup the instance of $interval with any repeated functions, so the function passed to forEach in which the error is thrown is never executed. The test failed when a repeated task was added.

This pull requests prevents the runtime exception by returning from cancel() immediately if no promise is supplied (doesn't even get to the loop) and improves the test by setting up a repeating task as the other tests do.

[mary-poppins]

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[dluxemburg]

Whoops sorry. Just did so.

[mary-poppins]

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[dluxemburg]

Thanks! (Tag still says 'cla: no' though)

[mary-poppins]

CLA signature verified! Thank you!

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