Merge branch 'fix-error-500-global-search-issues' into 'master'

Fix Error 500 when doing a search in dashboard before visiting any project

If a search turned up an issue, under certain conditions you would see this error:

```
ActionView::Template::Error (undefined method `path_with_namespace' for nil:NilClass):
     6:   - if issue.description.present?
     7:     .description.term
     8:       = preserve do
     9:         = search_md_sanitize(markdown(issue.description))
    10:   %span.light
    11:     #{issue.project.name_with_namespace}
    12:   - if issue.closed?
  lib/gitlab/markdown/upload_link_filter.rb:36:in `build_url'
  lib/gitlab/markdown/upload_link_filter.rb:31:in `process_link_attr'
  lib/gitlab/markdown/upload_link_filter.rb:18:in `block in call'
  lib/gitlab/markdown/upload_link_filter.rb:17:in `call'
  lib/gitlab/markdown.rb:127:in `gfm'
  lib/gitlab/markdown.rb:24:in `render'
  app/helpers/gitlab_markdown_helper.rb:61:in `markdown'
  app/views/search/results/_issue.html.haml:9:in `block in _app_views_search_results__issue_html_haml__4127460390996300432_59973760'
  app/views/search/results/_issue.html.haml:8:in `_app_views_search_results__issue_html_haml__4127460390996300432_59973760'
  app/views/search/_results.html.haml:20:in `_app_views_search__results_html_haml__589475855773452465_61761440'
  app/views/search/show.html.haml:5:in `_app_views_search_show_html_haml___1852335078065998536_69780120'
```

Confirmed this is issue still happens in GitLab 8.4, and it also happens on GitLab.com. Here's how to reproduce:

1. Login in a new browser.
2. Enter a search term on the top right that will land a hit in the "Issues" (e.g. GitLab).
3. Click on "Issues" tab. You should get an Error 500.

The issue is that @project isn't assigned to anything.

See merge request !2110

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
 v 8.3.0 (unreleased)
+v 8.4.0 (unreleased)
+  - Fix Error 500 when doing a search in dashboard before visiting any project (Stan Hu)
+  - Implement new UI for group page
+  - Add project permissions to all project API endpoints (Stan Hu)
+
+v 8.3.0
+  - Add CAS support (tduehr)
   - Bump rack-attack to 4.3.1 for security fix (Stan Hu)
   - API support for starred projects for authorized user (Zeger-Jan van de Weg)
   - Add open_issues_count to project API (Stan Hu)

app/views/search/results/_issue.html.haml

@@ -6,7 +6,7 @@
   - if issue.description.present?
     .description.term
       = preserve do
-        = search_md_sanitize(markdown(issue.description))
+        = search_md_sanitize(markdown(issue.description, { project: issue.project }))
   %span.light
     #{issue.project.name_with_namespace}
   - if issue.closed?