Do not crash if an app does not have a redis service config

src/addons.js

@@ -1835,7 +1835,7 @@ function setupRedis(app, options, callback) {
     assert.strictEqual(typeof options, 'object');
     assert.strictEqual(typeof callback, 'function');
 
-    if (app.servicesConfig['redis'].disabled) return appdb.unsetAddonConfig(app.id, 'redis', callback);
+    if (app.servicesConfig['redis'] && app.servicesConfig['redis'].disabled) return appdb.unsetAddonConfig(app.id, 'redis', callback);
 
     const redisName = 'redis-' + app.id;