make sure that `sensitive` is a boolean - fixes #596

Some remote instances may send garbage. If the `sensitive` value
passed to `driveService.uploadFromUrl` is not a boolean, eventually
we'll get an exception from the database complaining about that. This
change avoids that problem.

packages/backend/src/core/activitypub/models/ApImageService.ts

@@ -82,7 +82,7 @@ export class ApImageService {
 			url: image.url,
 			user: actor,
 			uri: image.url,
-			sensitive: image.sensitive,
+			sensitive: !!(image.sensitive),
 			isLink: !shouldBeCached,
 			comment: truncate(image.name ?? undefined, DB_MAX_IMAGE_COMMENT_LENGTH),
 		});