Error Cannot read property 'playBellSound' of undefined after reloading window with hidden terminal

[jeanp413]

• VS Code Version: From sources
• OS Version:

Steps to Reproduce:

1. Set "terminal.integrated.enableBell": true
2. Focus terminal and type Ctrl+G to trigger bell sound
3. Hide terminal panel
4. Reload window
5. 🐛 The following error shows in dev tools

Uncaught TypeError: Cannot read property 'playBellSound' of undefined
    at t.bell (Terminal.ts:1175)
    at Terminal.ts:153
    at e.fire (EventEmitter.ts:67)
    at t.bell (InputHandler.ts:786)
    at Object.<anonymous> (InputHandler.ts:369)
    at r.parse (EscapeSequenceParser.ts:670)
    at t.parse (InputHandler.ts:574)
    at e._action (CoreTerminal.ts:65)
    at e._innerWrite (WriteBuffer.ts:169)
    at WriteBuffer.ts:140

[jeanp413]

Created xtermjs/xterm.js#3314 fixing this