Handle hosts that have not had details updated in "Hosts" table (#642)

- Render "Never" in the "Last fetched" column if the value of `detail_updated_at` is improbable.
Resolves #639

frontend/kolide/helpers.ts

@@ -291,6 +291,13 @@ export const humanHostMemory = (bytes: number): string => {
 };
 
 export const humanHostDetailUpdated = (detailUpdated: string): string => {
+  // Handles the case when a host has checked in to Fleet but
+  // its details haven't been updated.
+  // July 28, 2016 is the date of the initial commit to kolide/fleet.
+  if (detailUpdated < "2016-07-28T00:00:00Z") {
+    return "Never";
+  }
+
   return moment(detailUpdated).fromNow();
 };