Fix endless loop while iterating with dict-fs

[manuelm]

We need to stop iterating if no key can be found.

This bug was introduced in 32e8bd5b5a9d5bc04e5ac6c65ac132ba5c386d64

[sirainen]

Thanks. I was wondering how that code came to be like that, but looks like it's a regression caused by 32e8bd5b5a9d5bc04e5ac6c65ac132ba5c386d64 in v2.3.17. (Oh, you had the commit hash already in the commit message, didn't notice that first.) I created internal DOP-2925 ticket for this.

[cmouse]

merged as 180a06ed49894af4a6dfad9c4959046928dfd117