Disable offline page when IndexedDB isn't available

assets/javascripts/app/db.coffee

@@ -109,16 +109,14 @@ class app.DB
 
   versions: (docs, fn) ->
     @db (db) ->
-      result = {}
-
       unless db
-        result[doc.slug] = false for doc in docs
-        fn(result)
+        fn(false)
         return
 
       txn = db.transaction ['docs'], 'readonly'
       txn.oncomplete = -> fn(result)
       store = txn.objectStore('docs')
+      result = {}
 
       docs.forEach (doc) ->
         req = store.get(doc.slug)

assets/javascripts/collections/docs.coffee

@@ -37,6 +37,7 @@ class app.collections.Docs extends app.Collection
 
   getDownloadStatuses: (callback) ->
     app.db.versions @models, (statuses) ->
-      for key, value of statuses
-        statuses[key] = downloaded: !!value, version: value
+      if statuses
+        for key, value of statuses
+          statuses[key] = downloaded: !!value, version: value
       callback(statuses)

assets/javascripts/templates/error_tmpl.coffee

@@ -22,6 +22,11 @@ app.templates.bootError = ->
         """ Check your Internet connection and try <a href="javascript:location.reload()">reloading</a>.<br>
             If you keep seeing this, you're likely behind a proxy or firewall that blocks cross-domain requests. """
 
+app.templates.offlineError = ->
+  error """ Your browser is unsupported, sorry. """,
+        """ DevDocs uses IndexedDB to cache complete documentations for offline access.<br>
+            Unfortunately your browser either doesn't support IndexedDB, or its implementation is buggy. """
+
 app.templates.unsupportedBrowser = """
   <div class="_fail">
     <h1 class="_fail-title">Your browser is unsupported, sorry.</h1>

assets/javascripts/views/content/offline_page.coffee

@@ -11,9 +11,12 @@ class app.views.OfflinePage extends app.View
 
   render: ->
     app.docs.getDownloadStatuses (statuses) =>
-      html = ''
-      html += @renderDoc(doc, statuses[doc.slug]) for doc in app.docs.all()
-      @html @tmpl('offlinePage', html)
+      if statuses is false
+        @html @tmpl('offlineError')
+      else
+        html = ''
+        html += @renderDoc(doc, statuses[doc.slug]) for doc in app.docs.all()
+        @html @tmpl('offlinePage', html)
       return
     return