Fix signed/unsigned comparison statements.
When a network interface of a path is down, bandwith of the concerned peer isn't published with a value tending toward zero as expected. It's caused by a signed/unsigned comparison.
As rist_send_seq_rtcp
relies on sendmsg
and sendto
it can return only -1
on error as mentionned by their man pages.
Consequently, checking errors can be implemented with this statement: if (ret == (size_t)-1)