A small circle on the top right layout

### Issue type

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

* [ x] bug report
* [ ] feature request

### Issue description

**Current behavior:**

There's a small circle on the top right layout every time when loading the page.
It also appears on the documentation website, for example, https://akveo.github.io/nebular/docs/components/sidebar/overview#nbsidebarcomponent

**Expected behavior:**
How to remove that small circle? It's become a UI issue in my project.

**Steps to reproduce:**
- Go to any page of https://akveo.github.io/nebular
- There's a small circle on the top right of the page
- It appears a few seconds
- If we hard refresh the page, it always shows

**Related code:**
I couldn't inspect it because it appears on the first loading page only.

```
insert short code snippets here
```

### Other information:

**npm, node, OS, Browser**
```
Node, npm: `v12.13.0` and `6.14.8`
OS: macOS Catalina
Browser: Chrome
```

**Angular, Nebular**
```
"dependencies": {
"@akveo/ng2-completer": "^9.0.1",
"@angular/animations": "^11.0.9",
"@angular/cdk": "11.0.4",
"@angular/common": "^11.0.9",
"@angular/compiler": "^11.0.9",
"@angular/core": "^11.0.9",
"@angular/fire": "^6.1.4",
"@angular/forms": "^11.0.9",
"@angular/google-maps": "^11.0.4",
"@angular/localize": "^11.0.5",
"@angular/platform-browser": "^11.0.9",
"@angular/platform-browser-dynamic": "^11.0.9",
"@angular/router": "^11.0.9",
"@asymmetrik/ngx-leaflet": "3.0.1",
"@nebular/auth": "7.0.0",
"@nebular/eva-icons": "7.0.0",
"@nebular/security": "7.0.0",
"@nebular/theme": "7.0.0",
"@ng-bootstrap/ng-bootstrap": "^9.1.0",
"@ngx-translate/core": "^13.0.0",
"@ngx-translate/http-loader": "^6.0.0",
"@swimlane/ngx-charts": "^14.0.0",
"@swimlane/ngx-datatable": "^19.0.0",
"@tinymce/tinymce-angular": "^4.2.2"
}
```