pick should use array_key_exists instead of isset

[lorenzomar]

pick source code use isset to check if the given key is present in the collection. This implies that NULL values are not valid but they should be. What about to use array_key_exists?

[lstrojny]

The behavior difference would be in case you have a default value other than null specified, right?

[lorenzomar]

Hey lstrojny, so sorry for the delay.
From a pragmatic point of view you're right but i think that the real difference is more conceptual. isset doesn't consider null as a valid value but there are cases where a collection contains a mix of null values, falsy value, etc and they are all right.
In that cases current implementation of pick fails.

[lstrojny]

Makes all sense, should indeed be array_key_exists. Want to open a PR for it?