Quotation of RFC3986:
A percent-encoded octet is encoded as a character
triplet, consisting of the percent character "%" followed by the two
hexadecimal digits representing that octet's numeric value
So test the length of the return of OString::number and add "0" if needed

ScEncodeURL was added with:
https://cgit.freedesktop.org/libreoffice/core/commit/?id=25434372bf56e0ebdb7e7d47ab3c14c68211509f

Thank you to Bele (the bugtracker reporter) for code pointer!

Change-Id: I8df102eb38b31933c6ebb15bb25c125b423f722b
Reviewed-on: https://gerrit.libreoffice.org/41086Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Eike Rathke <erack@redhat.com>