Backfill release dates on startup and hard-lock undated lessons

src/colossiansStudy.tsx

@@ -79,9 +79,9 @@ function isComingSoon(section: StudySection): boolean {
 }
 
 function isSectionReleased(section: StudySection): boolean {
-  if (!section.releasedAt) return true
+  if (!section.releasedAt) return false
   const releaseDate = new Date(section.releasedAt)
-  if (Number.isNaN(releaseDate.getTime())) return true
+  if (Number.isNaN(releaseDate.getTime())) return false
   return releaseDate <= new Date()
 }