Handle non-existent resources explicitly

Signed-off-by: Yasin Özel <yozel@nebius.com>

Author: yozel

internal/action/diff.go

@@ -42,6 +42,7 @@ import (
 	ssautil "github.com/fluxcd/pkg/ssa/utils"
 
 	v2 "github.com/fluxcd/helm-controller/api/v2"
+
 	"github.com/fluxcd/helm-controller/internal/diff"
 )
 
@@ -297,7 +298,10 @@ func (s sortableDiffs) Less(i, j int) bool {
 func replaceDisallowedFieldManagers(ctx context.Context, c client.Client, fieldOwner string, disallowedFieldManagers []string, obj *unstructured.Unstructured) error {
 	existingObj := &unstructured.Unstructured{}
 	existingObj.SetGroupVersionKind(obj.GroupVersionKind())
-	if err := c.Get(ctx, client.ObjectKeyFromObject(obj), existingObj); client.IgnoreNotFound(err) != nil {
+	if err := c.Get(ctx, client.ObjectKeyFromObject(obj), existingObj); err != nil {
+		if apierrors.IsNotFound(err) {
+			return nil
+		}
 		return err
 	}