fix(editor): Fix local storage flags defaulting to undefined string (#7603)

useStorage takes the default value `undefined` and sets it in local
storage.. also returns "undefined" as string which breaks onboarding
flows

Github issue / Community forum post (link here to close automatically):

packages/editor-ui/src/composables/useStorage.test.ts

@@ -0,0 +1,48 @@
+import { nextTick } from 'vue';
+import { useStorage } from './useStorage';
+
+describe('useStorage', () => {
+	beforeEach(() => {
+		localStorage.clear();
+	});
+
+	it('should initialize with null if no value is stored in localStorage', () => {
+		const key = 'test-key';
+		const data = useStorage(key);
+
+		expect(data.value).toBeNull();
+	});
+
+	it('should initialize with the stored value if it exists in localStorage', () => {
+		const key = 'test-key';
+		const value = 'test-value';
+		localStorage.setItem(key, value);
+
+		const data = useStorage(key);
+		expect(data.value).toBe(value);
+	});
+
+	it('should update localStorage when the data ref is updated', async () => {
+		const key = 'test-key';
+		const value = 'test-value';
+		const data = useStorage(key);
+
+		data.value = value;
+		await nextTick();
+
+		expect(localStorage.getItem(key)).toBe(value);
+	});
+
+	it('should remove the key from localStorage when the data ref is set to null', async () => {
+		const key = 'test-key';
+		const value = 'test-value';
+		localStorage.setItem(key, value);
+
+		const data = useStorage(key);
+
+		data.value = null;
+		await nextTick();
+
+		expect(localStorage.getItem(key)).toBeNull();
+	});
+});