Erro Ionic and Firebase when inputs is empty


I’m new to Ionic and I’m building an app with Firebase and I have not found my doubt in previous topics. I made a normal CRUD by connecting Firebase and Ionic, but whenever I add a new data if I leave a input or all empty inputs Ionic shows an error (I think Firebase expected to wait for something and did not receive it). I would like to know, how is the conditional when the inputs are empty? Or are there any other special settings? I want it to be sent to Firebase data even if blank.

Code Add:
addItem(item: Item){
this.humor.addItem(item).then(ref => {‘Seu humor foi adicionado com sucesso!’);
this.navCtrl.setRoot(AboutPage, {key: ref.key})