fix(history): fix updateHistoryEntryTimestamp to handle nullable user

If a user is null it means we're handling a guest user.

Signed-off-by: Philip Molares <philip.molares@udo.edu>

src/history/history.service.spec.ts

@@ -7,6 +7,7 @@ import { ConfigModule } from '@nestjs/config';
 import { EventEmitterModule } from '@nestjs/event-emitter';
 import { Test, TestingModule } from '@nestjs/testing';
 import { getDataSourceToken, getRepositoryToken } from '@nestjs/typeorm';
+import assert from 'assert';
 import { Mock } from 'ts-mockery';
 import { DataSource, EntityManager, Repository } from 'typeorm';
 
@@ -205,6 +206,7 @@ describe('HistoryService', () => {
           Note.create(user, alias) as Note,
           user,
         );
+        assert(createHistoryEntry != null);
         expect(await (await createHistoryEntry.note).aliases).toHaveLength(1);
         expect((await (await createHistoryEntry.note).aliases)[0].name).toEqual(
           alias,
@@ -225,6 +227,7 @@ describe('HistoryService', () => {
           Note.create(user, alias) as Note,
           user,
         );
+        assert(createHistoryEntry != null);
         expect(await (await createHistoryEntry.note).aliases).toHaveLength(1);
         expect((await (await createHistoryEntry.note).aliases)[0].name).toEqual(
           alias,
@@ -237,6 +240,10 @@ describe('HistoryService', () => {
         );
       });
     });
+    it('returns null if user is null', async () => {
+      const entry = await service.updateHistoryEntryTimestamp({} as Note, null);
+      expect(entry).toBeNull();
+    });
   });
 
   describe('updateHistoryEntry', () => {

src/history/history.service.ts

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
  *
  * SPDX-License-Identifier: AGPL-3.0-only
  */
@@ -74,13 +74,16 @@ export class HistoryService {
    * Updates the updatedAt timestamp of a HistoryEntry.
    * If no history entry exists, it will be created.
    * @param {Note} note - the note that the history entry belongs to
-   * @param {User} user - the user that the history entry belongs to
+   * @param {User | null} user - the user that the history entry belongs to
    * @return {HistoryEntry} the requested history entry
    */
   async updateHistoryEntryTimestamp(
     note: Note,
-    user: User,
+    user: User | null,
-  ): Promise<HistoryEntry> {
+  ): Promise<HistoryEntry | null> {
+    if (user == null) {
+      return null;
+    }
     try {
       const entry = await this.getEntryByNote(note, user);
       entry.updatedAt = new Date();