Tim Kosse points out that xfer_upload_gotpkt can return a negative

value on error, so the check at the call site shouldn't test for
exactly zero.

[originally from svn r8183]

psftp.c

@@ -707,7 +707,7 @@ int sftp_put_file(char *fname, char *outfname, int recurse, int restart)
 	if (!xfer_done(xfer)) {
 	    pktin = sftp_recv();
 	    ret = xfer_upload_gotpkt(xfer, pktin);
-	    if (!ret) {
+	    if (ret <= 0 && !err) {
 		printf("error while writing: %s\n", fxp_error());
 		err = 1;
 	    }