Use ci_commits.gl_project_id instead of ci_builds.gl_project_id:

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5142#note_13125513

app/models/project.rb

@@ -437,10 +437,11 @@ class Project < ActiveRecord::Base
     commit_object = commit(ref)
     if commit_object.nil?
-      builds.none
+      Ci::Build.none
     else
-      builds.joins(:pipeline).
-        merge(Ci::Pipeline.where(sha: commit_object.sha))
+      Ci::Build.joins(:pipeline).
+        merge(Ci::Pipeline.where(sha: commit_object.sha,
+                                 project: self))
     end
   end