Dropdown selecting disabled option throws error using keyboard arrows

[JanuszMarek]

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Plunkr Case (Bug Reports)
https://github-y88uxj.stackblitz.io

Current behavior
When some options are disabled and user wants to traverse to next enabled options using arrow down on keyboard an error is thrown in console. This does not occur when pressing arrow up.

Expected behavior
No error

Minimal reproduction of the problem with instructions

• Prepare SelectItem[] with some disabled items (already done in stackblitz link)
• Open dropdown
• Press arrow down on Keyboard
• Open Console
• There is an error
  ERROR TypeError: Cannot read property 'disabled' of undefined

Environment

• Angular version: 9.1.1

• PrimeNG version: 9.0.5
  Bug occurs also on newest PrimeNg site using 11.4.2

• Browser: Chrome 90.0.4430.212

• Language: TypeScript

• Node (for AoT issues): node --version = v14.16.1