ci: Fixed inefficiency in the findRootCause method

[shawabhijit]

The fix improves efficiency by:

Adding a null/empty check to handle edge cases gracefully Still using the first path to create the initial set of coordinates Using Guava's Sets.intersection() method instead of repeated retainAll() calls This creates new intersection sets rather than modifying the original set in-place The result is a more efficient implementation that scales better with larger numbers of dependency paths and larger sets