Custom interceptor is not called

### Issue type

**I'm submitting a ...** (check one with "x")

* [x] bug report
* [ ] feature request
* [ ] question about the decisions made in the repository

### Issue description

**Current behavior:**
I have a custom interceptor of angular included in AppModule, when I update the ngx-admin, the interceptor is not working, it is not called in several routes or it is call more than once.

**Expected behavior:**
The interceptor should be called in every call.

**Steps to reproduce:**
Update ngx-admin to last release.

**Related code:**

```
providers: [
{ provide: APP_BASE_HREF, useValue: '/' },
{ provide: HTTP_INTERCEPTORS, useClass: AppInterceptor, multi: true, deps: [Router, AlertService] }
],
```

### Other information:

**npm, node, OS, Browser**
```
# node --version
v8.11.3

# npm --version
6.4.1

```

**Angular, Nebular**
```
"@angular/core": "6.0.0",
"@nebular/auth": "2.0.1"
```