set _framebuffer even when null
set _framebuffer even when null

sebavan/Babylon.js,BabylonJS/Babylon.js,sebavan/Babylon.js,RaananW/Babylon.js,RaananW/Babylon.js,RaananW/Babylon.js,sebavan/Babylon.js,BabylonJS/Babylon.js,BabylonJS/Babylon.js