fix: modified QueueGetters.getJob and Job.fromId to also return null to

maintain consistency with v3 API.

src/classes/job.ts

@@ -135,7 +135,7 @@ export class Job<T = any, R = any> {
     return job;
   }
 
-  static async fromId(queue: QueueBase, jobId: string) {
+  static async fromId(queue: QueueBase, jobId: string): Promise<Job | null> {
     // jobId can be undefined if moveJob returns undefined
     if (jobId) {
       const client = await queue.client;

src/classes/queue-getters.ts

@@ -6,7 +6,7 @@ import { Job } from './job';
 import { clientCommandMessageReg } from './worker';
 
 export class QueueGetters extends QueueBase {
-  getJob(jobId: string) {
+  getJob(jobId: string): Promise<Job | null> {
     return Job.fromId(this, jobId);
   }