Cannot read property 'outlets' of null

Question

I have next problem : Cannot read property 'outlets' of null. My project works, but after some time it stopped working, but i didn't change my code. Help me please.
Update
My component with router-outlet:

import { Component } from '@angular/core';

@Component({
  selector: 'app',
  template: '
    <nav-menu></nav-menu>
    <router-outlet></router-outlet>
    <footer-component></footer-component>

',
})
export class AppComponent  {}

app.module:

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { RouterModule } from '@angular/router';
import { LocationStrategy, PathLocationStrategy, APP_BASE_HREF } from       '@angular/common';
import { HttpModule } from '@angular/http';
import {FormsModule,ReactiveFormsModule} from '@angular/forms';
//+components
@NgModule({
    imports:
    [
        BrowserModule,
        HttpModule,
        FormsModule,
        ReactiveFormsModule,
        RouterModule.forRoot([
            { path: '', component: HomeComponent },
            { path: 'home', component: HomeComponent },
            { path: 'blog', component: BlogComponent },
            { path: '2016/:link', component: BlogArticleFullComponent },
            {
                path: 'admin', component: AdminComponent, 
                children: [
                    { path: 'new', component: NewArticleComponent },
                    { path: 'new-writer', component: NewWriterComponent },
                    { path: 'new-tag', component: NewTagComponent }
                ] },
            { path: '**', redirectTo: '', pathMatch: 'full'}
        ])
    ],
    declarations:
    [//components
    ],
    bootstrap:
    [
        AppComponent
    ],
    providers:
    [
        { provide: APP_BASE_HREF, useValue: '/' },
        { provide: LocationStrategy, useClass: PathLocationStrategy }
    ]
})
export class AppModule { }

P.S. There is ' quote against ` because stackoverflow ``-is code.

Answer 1

For future reference: I got this error when using [routerLink] with an array which looked like ['/foo', null]. Fixed it by supplying an object instead of null.