Karma sometimes returns a transient state with zero tests. This is a recoverable state, so we shouldn’t be reporting an error to the github test status app.

To fix this:

• Find the karmaBrowserComplete_ function in build-system/tasks/runtime-test/helpers.js
• Remove the call to reportTestErrored
• Update the comment to reflect the fact that a warning is printed, but an error state is not reported

/cc @erwinmombay (who reported this a few days ago)