Fix handling of entries with no title

[Terrance]

pykeepass appears to set Entry.title to None when an entry's title is left blank (for example, in generated entries that weren't subsequently filled in with more details).

Here are a couple of fixes to handle possibly-None titles when listing and searching -- I've not exhaustively tried all commands, but I think this covers everywhere where title is assumed to be str.

[cizmazia]

Merged, thank you!