Fix check for missing speedIndex from WPT.
Fix check for missing speedIndex from WPT.

After the previous patch we get ”ERROR: Error creating WebPageTest result Error: Tried to add undefined to stats for path firstView,SpeedIndex” errors.
The check for SpeedIndex <=0 doesn’t work. With this commit we normalize undefined to 0 before checking <= 0.

sitespeedio/sitespeed.io,sitespeedio/sitespeed.io,sitespeedio/sitespeed.io,beenanner/sitespeed.io,beenanner/sitespeed.io,beenanner/sitespeed.io,sitespeedio/sitespeed.io