receiver: fix panic by initializing last seen file

tridge rsync declares “static uid_t uid;”, i.e. initializes uid=0.
This means when running as root, rsync does not need to transfer
the uid and can just set the XMIT_SAME_UID flag for the first entry.

related to #9

internal/receiver/flist.go

@@ -185,7 +185,7 @@ func (rt *Transfer) receiveFileEntry(flags uint16, last *File) (*File, error) {
 
 // rsync/flist.c:recv_file_list
 func (rt *Transfer) ReceiveFileList() ([]*File, error) {
-	var lastFileEntry *File
+	lastFileEntry := new(File)
 	var fileList []*File
 	for {
 		b, err := rt.Conn.ReadByte()