Crash when trying to add adjustment layer

[Cyrille Berger]

> Reproduce: Start Krita. Create a new image. Add an adjustment layer. Poof.
>
> It looks like the FastColorTransfer filter does something weird when called
> in the filter overview that ought to appear when one wants to add an
> adjustment layer.
not weird, it just doesn't check if it gets a null config. it's fixed now

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--- Cyrille Berger ---