This looks like a bug with that particular version of Aether II. At one point, Forge changed from empty ItemStacks being 'null' objects to being an itemless ItemStacks instead. Aether is still using the old logic and the version of Forge you are using does not support this. I'm not sure exactly when this change took place but see if there is a newer version of Aether II for 1.10.2.
I created a program that finds texture packs in the same directory and generates extensions of the packs for the mod Spectrite. In most cases, this just adds an overlay to existing textures. Since these textures are based on textures for existing packs, I'm just wondering whether there's a policy against uploading these on Curse/CurseForge. If so, is there some kind of disclaimer or additional credit I can add that would make them valid? I'd like to upload as many of these extensions as I can. Of course I know to avoid packs that don't allow modification of any kind, but I'm wondering even about the ones with less restrictive licenses.