NbSelect issue when using it with a template variable

[jgomesmv]

Issue type

**I'm submitting a:

• [x] bug report
• [ ] feature request

Issue description

Current behavior: When using the select component together with a template variable is causes and infinite loop on change detection if we try to access the selected value

Expected behavior: The component should work as expected and return undefined or null if no value is selected

Steps to reproduce:

<nb-select #values fullWidth placeholder="Select Import Type">
  <nb-option value=1>First</nb-option>
  <nb-option value=2>Second</nb-option>
</nb-select>

<p *ngIf="values.selected === 1">First Value Selected</p>

Related code: After looking at the source code I found out that select component tries do access selectionModel array while it is still undefined due to data loading. As a workarround we can do something like: <p *ngIf="values && values.selectionModel.length && values.selected === 1">First Value Selected</p>

Other information:

npm, node, OS, Browser

Node: v18.16.0 
npm: 9.5.1

Angular, Nebular

nebular: 11.0.0
angular: 15.2.8