Handle errors when reading build.boot

[danielcompton]

https://sentry.io/deps/versions/issues/404023447/

IllegalArgumentException: Don't know how to create ISeq from: clojure.lang.Symbol
    at jarkeeper.statuses$calculate_stats.invokeStatic(statuses.clj:102)
    at jarkeeper.statuses$calculate_stats.invoke(statuses.clj:99)
    at jarkeeper.statuses$boot_project_map.invokeStatic(statuses.clj:121)
    at jarkeeper.statuses$boot_project_map.invoke(statuses.clj:116)
    at jarkeeper.statuses$project_map$fn__9961.invoke(statuses.clj:160)
...
(20 additional frame(s) were not displayed)

ExecutionException: java.lang.IllegalArgumentException: Don't know how to create ISeq from: clojure.lang.Symbol
    at jarkeeper.statuses$project_map.invokeStatic(statuses.clj:161)
    at jarkeeper.statuses$project_map.invoke(statuses.clj:158)
    at jarkeeper.web$app_routes$fn__12359.invoke(web.clj:62)
    at jarkeeper.web$wrap_referrer_policy$fn__12375.invoke(web.clj:105)
...
(52 additional frame(s) were not displayed)