Assumes zero for all durations with empty file

If for some reason an empty timings file is ingested, the average duration for all the specs ends up 0, and all files are run in first node. Should the logic be updated to treat an empty file the same as no file existing?

Start by locating the code that ingests timings files and compare its empty-file path with the no-file path. Reproduce the case with an empty timings file, then add or update coverage so the resulting durations do not place every spec on the first node and verify the normal timings behavior remains unchanged.

Written by the indexing model from the issue text.