Merge branch 'dz-fix-group-milestone-creation' into 'master'

Fix 500 error when creating mileston from group page

Part of https://gitlab.com/gitlab-org/gitlab-ce/issues/23378

See merge request !6920

app/views/layouts/_init_auto_complete.html.haml

 - project = @target_project || @project
 - noteable_type = @noteable.class if @noteable.present?
 
-:javascript
-  GitLab.GfmAutoComplete.dataSource = "#{autocomplete_sources_namespace_project_path(project.namespace, project, type: noteable_type, type_id: params[:id])}"
-  GitLab.GfmAutoComplete.cachedData = undefined;
-  GitLab.GfmAutoComplete.setup();
+- if project
+  :javascript
+    GitLab.GfmAutoComplete.dataSource = "#{autocomplete_sources_namespace_project_path(project.namespace, project, type: noteable_type, type_id: params[:id])}"
+    GitLab.GfmAutoComplete.cachedData = undefined;
+    GitLab.GfmAutoComplete.setup();