I have stumbled across this thread:
In one post it is sugested that the error may be produced by the remote server not sending a notify before ending the tls connection. The following quote may be of interest:
Nikos said, "Several sites terminate the TLS connection without following the TLS protocol (i.e. sending closure alerts), but rather terminate the TCP connection directly. This is a relic of SSLv2 and it seems other implementations ignore this error. GnuTLS doesn't and thus prints this error. You could ignore it, but then you could not distinguish between a premature connection termination (i.e. by someone injecting a stray TCP termination packet) and normal termination."
Like i staded in an earlier post, the gnutls error itself does not seem to affectany functionality.