IndexedDiskCache: Mismatched memory and disk length (0) for [DED: pos = 63802 len = 9658] during optimization

I've created a small patch to test unit, that show the problem. See attached file.

Generally, the problem is, that when I insert more than elements into the Disk Cache, than it's limit, and then try to optimize it, there will be an IOException thrown:
Mismatched memory and disk length (0) for [DED: pos = 63802 len = 9658]