[orca-list] On Firefox: Orca tell me in table bottom pf column whereas I'm not at the end of a table

[Alex ARNAUD <alexarnaud hypra fr>]

Hello,

Environment:
- Debian 9 "Stretch"
- Orca master
- Firefox ESR 60.6.1 with e10s enabled

I've not exact steps to reproduce this and it's on a professional website.

I'll sent to Joanie a private debug log and incriminated webpage.

I hope if this issue is fixed it could help both Hypra's users and others.

Best regards,
Alex.