Fix exception on resource middle click in NEIE

[exyi]

In the Never Enough Items, middle click on a resource. This will navigate to the clicked resource, but also crashed the current Build process, because of modification of the iterated list.

Middle click on this:

... and error shows up:

Note that the middle click still works, it just an annoyance.

Solution is clone the List when replacing it's contents. Since its listy features are no longer required, I switched it to use an array instead.

[exyi]

Resolves #137, I guess

[exyi]

@DaleStan Thanks, I added the changelog.txt entry