PickList crashes Application when using SourceSelection

[master117]

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Codesandbox Case (Bug Reports)
https://codesandbox.io/s/goofy-platform-1jr8k

Minimal reproduction of the problem with instructions
Click on an Item: App crashes due to NPE.

The NPE is in PickList.js, the faulty commit is:
b0ac743

It's not checked whether this.state.sourceSelection exists, which it doesn't when the user supplies their own Source/TargetSelection