When navigating around, we make ajax requests with a parameter like `?filter=latest`. This results in the TopicQuery being set up with `filter: "latest"` as a string. The logic introduced in fd9a5bc0 checks for equality with `:latest` and `:unseen` symbols, which didn't work correctly in this situation
This commit makes the logic detect both strings and symbols, and adds a spec for the behaviour.
92bc61b4be