No filename for export on Inkscape instance without file

Summary:

In earlier versions, opening a new blank file sets the save path to /home/user/drawing.svg. This appears to be broken since inkscape!6140 (merged) (it wasn't working too well before that either, due to the bug the MR fixed).

Steps to reproduce:

• open Inkscape
• Open Export dialog

What happened?

(org.inkscape.Inkscape:998293): GLib-CRITICAL **: 02:31:30.476: g_canonicalize_filename: assertion 'relative_to == NULL || g_path_is_absolute (relative_to)' failed

The save path name is .png.

What should have happened?

Save path should have been /home/user/drawing.png

Version info

Inkscape 1.4-dev (18db810a6b, 2024-01-10)

                      Compile  (Run)
    GLib version:     2.78.1
    GTK version:      3.24.38 (3.24.38)
    glibmm version:   2.66.6
    gtkmm version:    3.24.8
    libxml2 version:  2.10.4
    libxslt version:  1.1.39
    Cairo version:    1.18.0 (1.18.0)
    Pango version:    1.51.0 (1.51.0)
    HarfBuzz version: 8.2.1 (8.2.1)

    OS version:       Fedora Linux 39 (Workstation Edition)