nil results panic (maybe a document expiry issue?)

[Leila-Codes]

On occasion some document results may return a valid key but the document value is nil.

Unfortunately I don't yet have a specific repeatable case but the theory/suspicion is:

1. JSON Document Added and Expiry is Set
2. Search is run
3. Document expires during query
4. Document returned has valid key, but value is nil.

This is unhandled when casting inside loadDocument() which completely crashes reading of data.

Proposed solution is to handle cast errors appropriately. Will submit a new PR shortly with implementation.