Remove ObjectValue.EMPTY (#3022)

Remove a dangling static reference.

Author: schmidt-sebastian

packages/firestore/src/model/object_value.ts

@@ -49,7 +49,6 @@ export const enum TypeOrder {
  * ability to add and remove fields (via the ObjectValueBuilder).
  */
 export class ObjectValue {
-  static EMPTY = new ObjectValue({ mapValue: {} });
 
   constructor(public readonly proto: { mapValue: api.MapValue }) {
     debugAssert(

packages/firestore/test/unit/model/object_value_builder.test.ts

@@ -27,7 +27,7 @@ describe('ObjectValueBuilder', () => {
   it('supports empty builders', () => {
     const builder = new ObjectValueBuilder();
     const object = builder.build();
-    expect(object.isEqual(ObjectValue.EMPTY)).to.be.true;
+    expect(object.isEqual(ObjectValue.empty())).to.be.true;
   });
 
   it('sets single field', () => {
@@ -109,7 +109,7 @@ describe('ObjectValueBuilder', () => {
     builder.set(field('foo'), wrap('foo'));
     builder.delete(field('foo'));
     const object = builder.build();
-    expect(object.isEqual(ObjectValue.EMPTY)).to.be.true;
+    expect(object.isEqual(ObjectValue.empty())).to.be.true;
   });
 
   it('sets and deletes nested field', () => {