Misc fix for feature-serverside-apply

staging/src/k8s.io/apiserver/pkg/endpoints/handlers/fieldmanager/internal/gvkparser.go

@@ -55,11 +55,15 @@ func newGVKParser(models proto.Models) (*gvkParser, error) {
 	for _, modelName := range models.ListModels() {
 		model := models.LookupModel(modelName)
 		if model == nil {
-			panic("ListModels returns a model that can't be looked-up.")
+			panic(fmt.Sprintf("ListModels returns a model that can't be looked-up for: %v", modelName))
 		}
 		gvkList := parseGroupVersionKind(model)
 		for _, gvk := range gvkList {
 			if len(gvk.Kind) > 0 {
+	                        _, ok := parser.gvks[gvk]
+                                if ok {
+                                    return nil, fmt.Errorf("Duplicate entry for %v", gvk)
+                                }
 				parser.gvks[gvk] = modelName
 			}
 		}