Accessing /plugins/git/<project_name>/<repo_name>?a=commit&h=invalid_ref
should not end up with a 500.
Trace:
PHP Fatal error: Uncaught Error: Call to a member function GetTree() on null in /usr/share/tuleap/plugins/git/include/GitPHP/controller/Controller_Commit.php:101
Stack trace:
#0 /usr/share/tuleap/plugins/git/include/GitPHP/controller/ControllerBase.php(241): Tuleap\Git\GitPHP\Controller_Commit->LoadData()
#1 /usr/share/tuleap/plugins/git/include/GitViews/GitPhpViewer.class.php(98): Tuleap\Git\GitPHP\ControllerBase->Render()
#2 /usr/share/tuleap/plugins/git/include/GitViews/GitPhpViewer.class.php(80): GitViews_GitPhpViewer->displayGitPHP()
#3 /usr/share/tuleap/plugins/git/include/GitViews/GitPhpViewer.class.php(67): GitViews_GitPhpViewer->displayContentWithoutEnclosingDiv()
#4 /usr/share/tuleap/plugins/git/include/GitViews/ShowRepo/Content.class.php(62): GitViews_GitPhpViewer->displayContent()
#5 /usr/share/tuleap/plugins/git/include/Git/GitRepositoryBrowserController.php(168): GitViews_ShowRepo_Content->display()
...