[pjsip] Division by 0 in pjmedia_rtcp_build_rtcp_xr(..)

[Johan Lantz]

Hi

I tried to activate rtcp_xr and after the call is disconnected I call 
pjsua_call_dump(..). When doing some calculations inside 
pjmedia_rtcp_build_rtcp_xr(..) the c13 value is 0 leading to a crash on 
the line below.

This is only FYI, I do not need this value and maybe there is some 
prereq in my kind of call that is not fullfilled in order to actually 
calculate the XR values. I just wanted to inform you about the crash in 
case there is room for improvments.

/* Calculate burst and gap durations in ms */
        sess->stat.rx.voip_mtc.gap_dur = (pj_uint16_t)((c11+c14+c13)*m/c13);

The values when entering the /* Voip Metrics Block */ are:
    pj_uint32_t c11 = 112
    pj_uint32_t c13 = 0
    pj_uint32_t c14 = 2
    pj_uint32_t c22 = 2
    pj_uint32_t c23 = 1
    pj_uint32_t c31 = 0
    pj_uint32_t c32 = 1
    pj_uint32_t c33 = 0

Best Regards

Johan