Object to Path and Stroke to Path assign wrong fill for nested Tspans

Summary:

For nested Tspans that inherit their fill from an ancestor, Object to Path and Stroke to Path can assign the wrong fill. Stroke seems to be unaffected.

Steps to reproduce:

Run Stroke to Path on . Both the 'eff' and the '5 μ' will be black instead of white.

Version info

Inkscape 1.2.1 (9c6d41e410, 2022-07-14)

    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: 4.4.1

    OS version:       Windows 10 22H2

Inkscape 1.3-dev (4435d25a6, 2023-03-12)

    GLib version:     2.74.6
    GTK version:      3.24.37
    glibmm version:   2.66.5
    gtkmm version:    3.24.7
    libxml2 version:  2.10.3
    libxslt version:  1.1.37
    Cairo version:    1.17.7
    Pango version:    1.50.14
    HarfBuzz version: 7.1.0

    OS version:       Windows 10 22H2