Missposition of dialog when rendering from background thread

### Issue type

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

* [ x] bug report
* [ ] feature request

### Issue description

**Current behavior:**
When rendering a dialog using the dialogService from a background thread, UI gets corrupted

**Expected behavior:**
The dialog renders properly

**Steps to reproduce:**
Configure remote notifications or any data from a background service. Then render a dialog with the response.

### Other information:

**npm, node, OS, Browser**
```
Chrome Version 81.0.4044.138
Mac OS
node -v : 14.5.0
```

**Angular, Nebular**
```
"@angular/cdk": "^9.1.2",
"@angular/common": "^9.0.4",
"@angular/compiler": "^9.0.4",
"@angular/core": "^9.0.4",

"@nebular/auth": "5.0.0",
"@nebular/eva-icons": "5.0.0",
"@nebular/security": "5.0.0",
"@nebular/theme": "5.0.0",

```