net.server_select: Fix possibility of losing data sent from a socket just before it closes (thanks Sjoerd Simons)

net/server.lua

@@ -467,7 +467,7 @@ wrapconnection = function( server, listeners, socket, ip, serverport, clientport
     end
     local _readbuffer = function( )    -- this function reads data
         local buffer, err, part = receive( socket, pattern )    -- receive buffer with "pattern"
-        if not err or ( err == "timeout" or err == "wantread" ) then    -- received something
+        if not err or string_len(part) > 0 then    -- received something
             local buffer = buffer or part or ""
             local len = string_len( buffer )
             if len > maxreadlen then