In my usage list(settings>general>storage & iCloud usage>manage storage), there is an app that registers as (null) with no icon, a version number that doesn't match anything I've previously downloaded, and it's taking up storage space. I first noticed it about a week or two ago. And no, I can't download recent apps to find the one that it is, because I downloaded multiple apps recently, and didn't notice the (null) app until my storage was critically low and I was looking to delete something. I am running iOS 9.2.1 on an iPhone 5C.
You can try this way:
- View the apps you deleted
- Find the app which about the same size with NULL app or version that match to the "Null" version
- Download the app again
- Remove it again and delete the cache
Hope it works for you.