Nb-layout-header causing ng test to fail

### Issue type

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

* [x] bug report
* [ ] feature request

### Issue description

**Current behavior:**
This bug only appears while testing, and only in components which contain the nb header component. The app works fine, it's purely an error I get while testing.

**Expected behavior:**
The test would pass (as the app works fine, this seems logical, and all other nb-layout tags work fine)

**Steps to reproduce:**
Use nb-layout-header in any component, ng test, errors out. To be clear, I am familiar with angular spec files, this app has lots of tests, all of which work fine, I know how to import modules, etc.

**Related code:**
``````

A sample application via GitHub

StackBlitz [StackBlitz Seed Project](https://stackblitz.com/github/akveo/nebular-seed)

-->

```
insert short code snippets here
```

### Other information:

**npm, node, OS, Browser**
```

```

**Angular, Nebular**
```
{
"name": "service-planning-front-end",
"version": "0.0.0",
"scripts": {
"ng": "ng",
"start": "ng serve",
"build": "ng build",
"test": "ng test",
"lint": "ng lint",
"e2e": "ng e2e"
},
"private": true,
"dependencies": {
"@angular/animations": "~8.2.14",
"@angular/cdk": "^8.0.0",
"@angular/common": "~8.2.14",
"@angular/compiler": "~8.2.14",
"@angular/core": "~8.2.14",
"@angular/forms": "~8.2.14",
"@angular/material": "^8.2.3",
"@angular/platform-browser": "~8.2.14",
"@angular/platform-browser-dynamic": "~8.2.14",
"@angular/router": "~8.2.14",
"@fortawesome/angular-fontawesome": "^0.5.0",
"@fortawesome/fontawesome-svg-core": "^1.2.26",
"@fortawesome/free-solid-svg-icons": "^5.12.0",
"@nebular/auth": "^4.5.0",
"@nebular/eva-icons": "^4.6.0",
"@nebular/theme": "^4.5.0",
"@ngrx/effects": "^8.5.2",
"@ngrx/schematics": "^8.5.2",
"@ngrx/store": "^8.0.0",
"@sentry/browser": "^5.11.1",
"eva-icons": "^1.1.1",
"husky": "^3.1.0",
"moment": "^2.24.0",
"moment-fquarter": "^1.0.0",
"moment-range": "^4.0.2",
"ngx-drag-to-select": "^3.1.1",
"precise-commits": "^1.0.2",
"rxjs": "~6.4.0",
"tslib": "^1.10.0",
"zone.js": "~0.9.1"
},
"husky": {
"hooks": {
"pre-commit": "precise-commits"
}
},
"devDependencies": {
"@angular-devkit/build-angular": "^0.803.23",
"@angular/cli": "^8.3.23",
"@angular/compiler-cli": "~8.2.14",
"@angular/language-service": "~8.2.14",
"@schematics/angular": "^8.3.23",
"@types/jasmine": "~3.3.8",
"@types/jasminewd2": "~2.0.3",
"@types/node": "~8.9.4",
"codelyzer": "^5.2.1",
"jasmine-core": "~3.4.0",
"jasmine-spec-reporter": "~4.2.1",
"karma": "~4.1.0",
"karma-chrome-launcher": "~2.2.0",
"karma-coverage-istanbul-reporter": "~2.0.1",
"karma-jasmine": "~2.0.1",
"karma-jasmine-html-reporter": "^1.4.0",
"prettier": "1.19.1",
"protractor": "~5.4.0",
"ts-node": "~7.0.0",
"tslint": "~5.15.0",
"typescript": "~3.5.3"
}
}

```