Don't pop an empty container, also use stol() so it does not throw
std::out_of_range.
Change-Id: Id81cb00ccfb0ecc234b8f6fa89edf5a0d8c6d353
Reviewed-on: https://gerrit.libreoffice.org/c/online/+/92524
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
