[smokeping-users] empty graph for DNS.pm and TCPPing.pm

[Xuefer]

FPing.pm works fine but DNS and TCPPing  is producing empty graph. i
failed to find the actual clause since i'm not a perl guy, but i
manage to workaround it by changnig "%.10e" into ".10f", can any
developer take a look into this?

reproduced with:
# perl --version

This is perl 5, version 28, subversion 1 (v5.28.1) built for x86_64-linux-glibc

Copyright 1987-2018, Larry Wall

# perl /usr/bin/smokeping --version
2.007003

or:

$ perl --version

This is perl 5, version 26, subversion 2 (v5.26.2) built for x86_64-linux
(with 28 registered patches, see perl -V for more detail)

$ perl /usr/bin/smokeping --version
2.006009