Add additional validation to push event

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

app/models/event.rb

@@ -168,7 +168,7 @@ class Event < ActiveRecord::Base
   end
 
   def valid_push?
-    data[:ref]
+    data[:ref] && ref_name.present?
   rescue => ex
     false
   end