1.0 RC1 crash on startup when default.svg contains older version string (from Inkscape 0.91)

Steps to reproduce:

• Reproducible with AppImage of 1.0 RC1 version: https://inkscape.org/gallery/item/18047/Inkscape-09960d6-x86_64.AppImage
• When the Inkscape user profile folder (in .config/inkscape/templates) contains a default.svg with a version string from an earlier Inkscape version than 0.92 (0.91.x-y-z) or an invalid version string, Inkscape crashes on startup with the following error message:

(org.inkscape.Inkscape:32292): glibmm-ERROR **: 03:59:09.418: 
unhandled exception (type std::exception) in signal handler:
what: basic_string::_M_construct null not valid

• Attached file producing the crash: default.svg
• Only version string changed, /no/ crash: default.svg

Inkscape Version and Operating System:

• Inkscape Version: 1.0rc1 (09960d6, 2020-04-09), from AppImage
• Operating System: Ubuntu 19.10 with KDE
• Operating System version: 19.10 x86-64 running Linux 5.3.0-46-generic kernel
• GTK3 version installed: 3.24.12-1ubuntu1
• GTK2 version installed: 2.24.32-4ubuntu1