Some nREPL `eval` messages are sent with `untitled` as `ns`

[PEZ]

Since we started to send proper eval nrepl ops, which include the ns parameter, we also sometimes send it as undefined. One reason this happens is the Calva repl.evaluateCode API, which doesn't have a documented way to provide the ns. So that API is broken right now, even if there's an undocumented workaround.