Looking at the diff between the two versions of sslKeyExchange.c released by Apple http://opensource.apple.com/source/Security/Security-55471/libsecurity_ssl/lib/sslKeyExchange.c and http://opensource.apple.com/source/Security/Security-55179.13/libsecurity_ssl/lib/sslKeyExchange.c
I was trying to come up with a reasonable explanations of how this could have happened, but failed.
Here the relevant part of the diff:
@@ -627,6 +628,7 @@
goto fail;
if ((err = SSLHashSHA1.update(&hashCtx, &signedParams)) != 0)
goto fail;
+ goto fail;
if ((err = SSLHashSHA1.final(&hashCtx, &hashOut)) != 0)
goto fail;