gitbase dies for query with WHERE NOT <not boolean value>

[zurk]

If you try to query something like:

select repository_id, commit_author_when, commit_parents from commits WHERE NOT commit_parents

gitbase dies. It is not a valid SQL query, because commit_parents type is not boolean, but I expect that gitbase remains available for new queries.

It is useful to have some general check if gitbase fails to process the query and do not shut down if the query was bad.

[smola]

I think it's ok to just check for bool on evaluation if you introduce the right CAST during analysis.