Export fails when there is no World node in blender

[metinc]

To recreate this bug:

1. Create a cube in blender
2. add a texture to it
3. delete the world node
4. export

[StanleySweet]

@gregeryb Maybe you could make a pull request ?

[gregdavisd]

@StanleySweet I did the thing, if it doesn't get merged here then there's the repository on my profile. The only difference is this fix. Lucky it was a 2 minute job, any longer I would have to demand payment in green jelly beans. https://github.com/gregeryb/collada-exporter

[StanleySweet]

Here is you jelly Bean mate. You deserved it :)