Prevent 500 if data[:commits] is nil for event

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/models/event.rb

@@ -223,7 +223,7 @@ class Event < ActiveRecord::Base
 
   # Max 20 commits from push DESC
   def commits
-    @commits ||= data[:commits].reverse
+    @commits ||= (data[:commits] || []).reverse
   end
 
   def commits_count