Using NbAuthModule login correctkly the first time, but after a logout, it shows an error

### Issue type

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

* [ X] bug report
* [ ] feature request

### Issue description
I used the example at the following link to authenticate an angular app with Azure B2C
https://github.com/akveo/nebular/tree/master/src/playground/without-layout/azure
when i try to login , it works correctly, then after logout it does not allow me to login again, with an error : "AADB2C: An exception has occurred"
**Current behavior:**

not login after the first logout
**Expected behavior:**

login/logout shall works
**Steps to reproduce:**

https://github.com/akveo/nebular/tree/master/src/playground/without-layout/azure
**Related code:**
NbAuthModule.forRoot({
strategies: [
AzureADB2CAuthStrategy.setup({
name: 'azure',
clientId: '4d*******************************',
clientSecret: '',
authorize: {
endpoint: 'https://A***.b2clogin.com/A*****.onmicrosoft.com/B2C_1_singin_signup/oauth2/v2.0/authorize',
responseType: 'id_token',
scope: 'openid',
redirectUri: 'http://localhost:4200/portal/callback',
params: {
p: 'B2C_1_singin_signup',
},
},
token: {
class: AuthAzureToken,
},
redirect: {
success: '/portal',
},
}),
],
}),

```
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### Other information:

**npm, node, OS, Browser**
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**Angular, Nebular**
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