fix agent crash when removing invalid image

pkg/client/image/remove.go

@@ -3,6 +3,7 @@ package image
 import (
 	"context"
 
+	"github.com/pkg/errors"
 	imagesv1 "github.com/rancher/kim/pkg/apis/services/images/v1alpha1"
 	"github.com/rancher/kim/pkg/client"
 	"github.com/sirupsen/logrus"
@@ -17,6 +18,9 @@ func (s *Remove) Do(ctx context.Context, k8s *client.Interface, image string) er
 		if err != nil {
 			return err
 		}
+		if ref == nil {
+			return errors.Errorf("image %q: not found", image)
+		}
 		res, err := imagesClient.Remove(ctx, &imagesv1.ImageRemoveRequest{Image: ref})
 		logrus.Debugf("%#v", res)
 		return err

pkg/server/images/remove.go

@@ -19,6 +19,9 @@ func (s *Server) Remove(ctx context.Context, req *imagesv1.ImageRemoveRequest) (
 		return nil, err
 	}
 	defer done(ctx)
+	if req.Image == nil {
+		return &imagesv1.ImageRemoveResponse{}, nil
+	}
 	img, err := s.Containerd.ImageService().Get(ctx, req.Image.Image)
 	if err != nil {
 		return nil, err