fix: reject instead of throwing on failed uploads

src/components/composer/lib/api.ts

···
 							}
 
 							if (!json.jobId) {
-								throw new PublishError(`Failed to upload video` + (json.error ? `: ${json.error}` : ''));
+								reject(new PublishError(`Failed to upload video` + (json.error ? `: ${json.error}` : '')));
+								return;
 							}
 
 							resolve(json.jobId);