apierrors: optimize ToAggregate() for zero-length lists

staging/src/k8s.io/apimachinery/pkg/util/validation/field/errors.go

@@ -239,6 +239,9 @@ func NewErrorTypeMatcher(t ErrorType) utilerrors.Matcher {
 
 // ToAggregate converts the ErrorList into an errors.Aggregate.
 func (list ErrorList) ToAggregate() utilerrors.Aggregate {
+	if len(list) == 0 {
+		return nil
+	}
 	errs := make([]error, 0, len(list))
 	errorMsgs := sets.NewString()
 	for _, err := range list {