Calendar extension should use number fields + unit, not text fields

Summary:

The Calendar extension in Inkscape 1.2.1 uses text fields for entering numbers with a unit. In consequence, it cannot work with localized decimal separators and renders invisible, zero-width text when I use a comma in one of those fields.

Steps to reproduce:

• open Inkscape
• Extensions > Render > Calendar: Layout : enter 12,5cm for width
• Apply

What happened?

No calendar visible:

What should have happened?

A calendar should have been rendered!

Version info

Inkscape 1.2.1 (1:1.2.1+202210291244+9c6d41e410)

    GLib version:     2.64.6
    GTK version:      3.24.20
    glibmm version:   2.64.2
    gtkmm version:    3.24.2
    libxml2 version:  2.9.10
    libxslt version:  1.1.34
    Cairo version:    1.16.0
    Pango version:    1.44.7
    HarfBuzz version: 2.6.4

    OS version:       Linux Mint 20.3