Upon init(), ZipFileSystem enumerates all the zip file entries and stores them in the global FilesCache as well as a "strongRef" array.
The ZipFileSystem implementation assumes that this will be sufficient to keep all entries in the cache, and so if the cache misses in AbstractFileSystem, ZipFileSystem assumes that the file does not exist and returns an imaginary file.
This implementation assumes that the WeakRefFilesCache is being used. If NullFilesCache or LRUFilesCaches is used, these assumptions will fail and ZipFileSystem will fail to resolve valid existing files within the system.
ZipFileSystem should maintain its own internal cache instead.