[Users] URL not passed to Firefox

[appakhabar]

Hello all

Lately, clicking on a link in an email does not result in the link
being passed to Firefox, which merely opens a blank window. This only
happened in the past couple of weeks.

Changing from "use system default" and choosing one of the firefox or
mozilla choices in Preferences > External programs doesn't work. Using
"qupzilla "%s" does open the URL. It's a minor inconvenience I can live
with, but it would be good to know how to restore the default behaviour.

System:
Claws-Mail 3.15.0, Firefox 59.0.2 (64-bit)
Mageia 6 version 4.14.25 on Thinkpad laptop

Regards.
-- 

G Rudra