Merge pull request #9838 from evindor/master

Fix github importer to handle empty issues

lib/gitlab/github_import/importer.rb

@@ -19,7 +19,7 @@ module Gitlab
           if issue.pull_request.nil?
             body = @formatter.author_line(issue.user.login)
-            body += issue.body
+            body += issue.body || ""
             if issue.comments > 0
               body += @formatter.comments_header