Got following issue

[albincs]

core.js:15724 ERROR TypeError: Cannot read property 'length' of undefined
at SafeSubscriber._next (tab2.page.ts:42)
at SafeSubscriber.push../node_modules/rxjs/_esm5/internal/Subscriber.js.SafeSubscriber.__tryOrUnsub (Subscriber.js:196)
at SafeSubscriber.push../node_modules/rxjs/_esm5/internal/Subscriber.js.SafeSubscriber.next (Subscriber.js:134)
at Subscriber.push../node_modules/rxjs/_esm5/internal/Subscriber.js.Subscriber._next (Subscriber.js:77)
at Subscriber.push../node_modules/rxjs/_esm5/internal/Subscriber.js.Subscriber.next (Subscriber.js:54)
at MapSubscriber.push../node_modules/rxjs/_esm5/internal/operators/map.js.MapSubscriber._next (map.js:41)
at MapSubscriber.push../node_modules/rxjs/_esm5/internal/Subscriber.js.Subscriber.next (Subscriber.js:54)
at FilterSubscriber.push../node_modules/rxjs/_esm5/internal/operators/filter.js.FilterSubscriber._next (filter.js:38)
at FilterSubscriber.push../node_modules/rxjs/_esm5/internal/Subscriber.js.Subscriber.next (Subscriber.js:54)
at MergeMapSubscriber.push../node_modules/rxjs/_esm5/internal/operators/mergeMap.js.MergeMapSubscriber.notifyNext (mergeMap.js:84)

[julianvasa]

What is the mainUrl in app/services/wordpress.service.ts?