combine: fix goroutine stack overflow on bad object

If the Remote() call failed to do its path adjustment, then it would
recursively call Remote() as part of logging the failure and cause a
stack overflow.

This fixes it by logging the underlying object instead.

See: https://forum.rclone.org/t/rclone-runtime-goroutine-stack-exceeds-1000000000-byte-limit/37912

backend/combine/combine.go

@@ -916,7 +916,7 @@ func (o *Object) String() string {
 func (o *Object) Remote() string {
 	newPath, err := o.u.pathAdjustment.do(o.Object.String())
 	if err != nil {
-		fs.Errorf(o, "Bad object: %v", err)
+		fs.Errorf(o.Object, "Bad object: %v", err)
 		return err.Error()
 	}
 	return newPath