Error at updating values with firebase

Ionic Framework ionic-v3
1 
import { Component } from '@angular/core';
import { IonicPage, NavController, NavParams } from 'ionic-angular';
import { Note } from '../../model/note';
import { NoteListService } from '../../services/note-list.service';

@IonicPage()
@Component({
  selector: 'page-edit-note',
  templateUrl: 'edit-note.html',
})
export class EditNotePage {

  note: Note = {
    key: '',
    title: '',
    content: ''
  };

  constructor(
    public navCtrl: NavController,
    public navParams: NavParams,
    private noteListService: NoteListService) {
  }

  ionViewDidLoad() {
    this.note = this.navParams.get('note');
  }

  updateNote(note: Note) {
    this.noteListService.updateNote(note).then(() => {
      this.navCtrl.setRoot('MeuCadastroPage');
    })
  }

  removeNote(note: Note) {
    this.noteListService.removeNote(note).then(() => {
      this.navCtrl.setRoot('MeuCadastroPage');
    })
  }
}

My note-list-service.ts:

import { Injectable } from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';
import { Note } from '../model/note';

@Injectable()
export class NoteListService {

    private noteListRef = this.db.list<Note>('note-list');

    constructor(private db: AngularFireDatabase) { }

    getNoteList() {
        return this.noteListRef;
    }

    addNote(note: Note) {
        return this.noteListRef.push(note);
    }

    updateNote(note: Note) {
        return this.noteListRef.update(note.key, note);
    }

    removeNote(note: Note) {
        return this.noteListRef.remove(note.key);
    }
}

My error: ''Reference.child failed: First argument was an invalid path = " . paths must be non empty.

2

put
this.note = this.navParams.get('note');
in constructor