Fixed RTP packet lost when seq == 0

[joeduff]

Describe the bug

file : pjmedia\src\pjmedia\rtp.c
function : pjmedia_rtp_seq_update
bug : if (seq == sess->max_seq+ 1)
modify : if (seq == (pj_uint16_t)(sess->max_seq+ 1))
describe :
seq = 0
==> sess->max_seq = 65535
if (seq == sess->max_seq+ 1)
==> if (0 == 65536)
if (seq == (pj_uint16_t)(sess->max_seq+ 1))
==> if (0 == 0)

Steps to reproduce

seq = 0

PJSIP version

master

Context

The issue happens on Windows linphone Desktop 5.0.18 - Qt5.15.2 Core 5.2.75

Log, call stack, etc

none

[sauwming]

Thanks for the suggestion. Since we're working on a related issue, I include the fix into #3653.