Fix hang in IO::Socket::INET.lines

Fixes R#1721 #1721

When we read zero bytes we ask the decoder for all it's got, which gives
us an empty string and we infiniloop "reading" all the empty strings.

Fix by checking if the decoder is empty before grabbing the last bytes.

src/core/IO/Socket.pm6

@@ -76,7 +76,8 @@ my role IO::Socket {
                 $line = $!decoder.consume-line-chars(:chomp);
                 last if $line.DEFINITE;
                 if $read == 0 {
-                    $line = $!decoder.consume-line-chars(:chomp, :eof);
+                    $line = $!decoder.consume-line-chars(:chomp, :eof)
+                        unless $!decoder.is-empty;
                     last;
                 }
             }