prevent app crash for events without git resources

app/models/event/push_trait.rb

@@ -63,5 +63,19 @@ module Event::PushTrait
         "pushed to"
       end
     end
+
+    def parent_commit
+      commits.first.prev_commit
+    rescue => ex
+      nil
+    end
+
+    def last_commit
+      commits.last
+    end
+
+    def push_with_commits? 
+      md_ref? && commits.any? && parent_commit && last_commit
+    end
   end
 end

app/views/events/_event_push.html.haml

@@ -10,10 +10,10 @@
     = time_ago_in_words(event.created_at)
     ago.
-  - if event.md_ref?
+  - if event.push_with_commits?
     - if event.commits.count > 1
-      = link_to compare_project_commits_path(event.project, :from => event.commits.first.prev_commit_id, :to => event.commits.last.id) do 
-        %strong #{event.commits.first.commit.id[0..7]}...#{event.commits.last.id[0..7]}
+      = link_to compare_project_commits_path(event.project, :from => event.parent_commit.id, :to => event.last_commit.id) do 
+        %strong #{event.commits.first.id[0..7]}...#{event.last_commit.id[0..7]}
     - project = event.project  
     %ul.unstyled.event_commits
       - if event.commits.size > 3