A path on Windows contains backslashes, which got interpreted as
escape sequences in script-fu when selecting a filename by the call
to g_string_append_printf.
This caused failures in e.g. Stencil Chrome after selecting an
environment map image.
Use script_fu_strescape to escape the filepath, so that we correctly
interpret the Windows path.
See also
https://gitlab.gnome.org/GNOME/gimp/-/merge_requests/1851#note_2225989