Fixed MAPBOX_KEY validation error

server/src/config/app.config.ts

@@ -13,9 +13,9 @@ export const immichAppConfig: ConfigModuleOptions = {
     JWT_SECRET: Joi.string().required(),
     ENABLE_MAPBOX: Joi.boolean().required().valid(true, false),
     MAPBOX_KEY: Joi.any().when('ENABLE_MAPBOX', {
-      is: true,
-      then: Joi.string().required(),
-      otherwise: Joi.string().optional(),
+      is: false,
+      then: Joi.string().optional().allow(null, ''),
+      otherwise: Joi.string().required(),
     }),
   }),
 };