Fix fatal: bad object 0000 when do new branch push

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

lib/gitlab_update.rb

@@ -23,8 +23,12 @@ class GitlabUpdate
   end
 
   def forced_push?
+    if @oldrev !~ /00000000/ && @newrev !~ /00000000/
       missed_refs = IO.popen(%W(git rev-list #{@oldrev} ^#{@newrev})).read
       missed_refs.split("\n").size > 0
+    else
+      false
+    end
   end
 
   def exec