Properly handle TLS disconnects in OpenSSLStream.leastSize.
Properly handle TLS disconnects in OpenSSLStream.leastSize.

Fixes bogus "Reading from TLS stream was unsuccessful with ret 0" errors.

etcimon/vibe.d,Geod24/vibe.d,rejectedsoftware/vibe.d,gedaiu/vibe.d,chalucha/vibe.d,etcimon/vibe.d