Bug. Disabled select can be expanded

[Matoosh]

Issue type

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

• [x] bug report
• [ ] feature request

Issue description

Current behavior: You can expand list on select component when it's disabled. Tested on Chrome, Chromium and Firefox. Worked only on FF.

Expected behavior: Disabled option should block expand list on select component on every browser.

Steps to reproduce:

1. Open Chrome or Chromium
2. Open https://akveo.github.io/nebular/example/select/select-disabled.component
3. Try expand Disabled select

Other information:

npm, node, OS, Browser

node --version ==> v14.15.2
npm --version  ==> 6.14.11
Windows 10 ==> 20H2 (19042.1466)
Chrome: 98.0.4758.81
Chromium: 92.0.4484.0 (Build)
Firefox: 96.0.3 (64-bit)

Angular, Nebular

    "@nebular/auth": "^9.0.0",
    "@nebular/bootstrap": "^9.0.0",
    "@nebular/date-fns": "^9.0.0",
    "@nebular/eva-icons": "^9.0.0",
    "@nebular/moment": "^9.0.0",
    "@nebular/security": "^9.0.0",
    "@nebular/theme": "^9.0.0",

[AdamWold]

Just ran into this, thanks for reporting it.