Regression from version 4.2.0a2 (d3a8d992e988)

To reproduce:
- Open attached project and launch "Splash" scene
- Hit Play snd wait until you can control the game
- Press the pause button in the top right corner in game
- Resume the game again.
- Observe the error message in Console:

m_PausedSources.empty()
UnityEngine.AudioListener:set_pause(Boolean)
SoundController:OnPauseGame(Boolean) (at Assets/_Scripts/Pebbles/System/Audio/SoundController.cs:348)
UnityEngine.GameObject:SendMessage(String, Object, SendMessageOptions)
GamePauser:PauseGame(Boolean) (at Assets/_Scripts/Game Logic/GamePauser.cs:35)
GamePauser:set_paused(Boolean) (at Assets/_Scripts/Game Logic/GamePauser.cs:10)
<DoUnpause>c__Iterator1E:MoveNext() (at Assets/_Scripts/Game Logic/GameplayLogic.cs:333)