Ignore non-exsitent date trees when scanning for new crashes.
Bug 805323 - Double-decode slashes in reasons parameter in search.
Merge pull request #1122 from rfw/empty_date_dirs

Don't throw an exception when we find a missing date dir.
Merge pull request #1123 from AdrianGaudebert/805323-allow-slashes-in-reasons

Bug 805323 - Double-decode slashes in reasons parameter in middleware.