I finally deleted the fping package (the ipv6 one).
pkg_delete from the previous post didn't work because it is replaced by pkg delete :
Code:
# pkg delete fping+ipv6-2.4b2
The following packages will be deinstalled:
fping+ipv6-2.4b2
The deinstallation will free 33 kB
Proceed with deinstalling packages [y/N]: y
Deleting fping+ipv6-2.4b2...pkg: fopen(/usr/local/man/man8/fping.8.gz): No such file or directory
done
# portmaster -a
===>>> Gathering distinfo list for installed ports
===>>> Starting check of installed ports for available updates
===>>> All ports are up to date