Hairline stroke width doesn't survive grouping

Summary:

When grouping, hairline strokes turn into non-hairline fixed width strokes.

Steps to reproduce:

• draw a rectangle
• pick a stroke color
• set the stroke width to hairline
• group it (ctrl-G)

What happened?

• the stroke width is no longer a hairline

What should have happened?

• the stroke width should still be a hairline

Demonstration

inkscape-hairline-problem

Version info

Inkscape 1.2 (dc2aedaf03, 2022-05-15)

    GLib version:     2.72.2
    GTK version:      3.24.34
    glibmm version:   2.66.4
    gtkmm version:    3.24.6
    libxml2 version:  2.9.14
    libxslt version:  1.1.35
    Cairo version:    1.17.6
    Pango version:    1.50.7
    HarfBuzz version: 4.3.0

    OS version:       Arch Linux