Fix deepClone edge case

test/deepClone.test.js

@@ -8,6 +8,8 @@ const a = { foo: 'bar', obj: { a: 1, b: 2 } };
 const b = deepClone(a);
 const c = [{ foo: 'bar' }];
 const d = deepClone(c);
+const e = { edge: [] };
+const f = deepClone(e);
 test('Shallow cloning works', () => {
   expect(a).not.toBe(b);
 });
@@ -20,3 +22,6 @@ test('Array shallow cloning works', () => {
 test('Array deep cloning works', () => {
   expect(c[0]).not.toBe(d[0]);
 });
+test('Array shallow cloning edge case works', () => {
+  expect(f.edge).toEqual([]);
+});