expected_error:0 fix a memory leak error reported by email in version <= 5.1.0
SIP/2.0 200! 0accept-encoding:000V;000, 06ccccc0000c; @ 0600;;;;;;;;;;; 06000t00(er, ,600ÿÿtdpZ00000000
authentication-info:00000From: <sip:000000/00000:::::00•;000=0000000000
proxy-authentication-info:00000nfo:0009sip0From:<sip:00000@Seq00000000080:0060;t ransport=UDP>
Content-Type: a00000a0i00/ent-Type: a00li000i0n/000
Call-Info:0<00t00000003000>;00000000000=0;0000=0000000l000;000=00000;0000=04000000a0i0ri0××××××××××××××××4o00=0
U000000000: 00C/00000
Content4Length:   394

v=0
o=02000 0 0 00 I00 00000000
s=000 S0i000
c=0N IP4 002000000000
t=0 0
k=00:00
m=a000o 20002 R000000 00000
k=00$m00:0000
k=00$m00:000000000000* 0ig0ate/