exception on game destroy after a scene has been restarted

[mbunby]

version: 3.11

example: https://codepen.io/anon/pen/EpoXPG?editors=1111

steps to reproduce

• starting with 'SceneA', click to change to 'SceneB'
• click again to change back to 'SceneA'
• press the 't' key to destroy the game instance

expected behaviour

when game.destroy() is called, the scene manager should destroy each scene's systems without throwing an error.

actual behaviour

throws the following exception:

phaser.js:114617 Uncaught TypeError: Cannot read property 'events' of null
at CameraManager.shutdown (phaser.js:114617)
at CameraManager.destroy (phaser.js:114633)
at EventEmitter.emit (phaser.js:2030)
at Systems.destroy (phaser.js:27523)
at SceneManager.destroy (phaser.js:47768)
at Game.runDestroy (phaser.js:109537)
at Game.step (phaser.js:109315)
at TimeStep.step (phaser.js:106091)
at step (phaser.js:66488)

[photonstorm]

Thank you for submitting this issue. We have fixed this and the fix has been pushed to the master branch. It will be part of the next release. If you get time to build and test it for yourself we would appreciate that.