GoodBoyDigital/pixi.js — pull request #1040 by SebastianNette (2014-10-14 00:01:46+00:00)
Title: Fix for Stage.setInteractionDelegate

If stage.setInteractionDelegate was used before rendering, then the WebGL Renderer will remove the events and revert to renderer.view.
That's why we should only remove the events if a stage was previously set.