Array with nulls

[jean343]

Hello,

Thanks for your fork, it helps me a lot!

I am having one issue with DeepExtend, it will merge arrays with null by removing the nulls.
For example, if we merge [{},null,{}] with itself, it will result in [{},{}], which is incorrect as the keys differs.

My proposed solution is to change the is_null to isUndefined in the array case of DeepExtend

Thanks!