GNUMail (svn build 947): openURL regression issue

Hello,

As I built again Pantomime and GNUMail from svn revision 947, I noted 
a regression about openURL.
- If I create a link within a TextEdit document and I click on it, it 
will launch Firefox and open the expected URL.
- If I click on a link within a message with GNUMail, it will produce 
a new kind of error. See the screenshot below.

<screenshot_2026-01-04_at_15:53:24.png>Closing the Firefox window will 
not open a new one nor a new tab with the expected URL.

Regards,
Patrick

-- 
Patrick Cardona - Pi400 - GNU/Linux aarch64 (Debian 13.2)
Xorg (1:7.7+24) - libcairo2 (1.18.4-1+rpt1 arm64)
Window Maker (0.96.0-4) - GWorkspace (1.1.0 - 02 2025) - Theme: 
AGNOSTEP - MUA: GNUMail (svn build)