Always check visibility on correct project for clone panel

The project variable can hold an object which is not an instance of
Project (e.g. ProjectWiki). In this case, visibility_level is not
defined.

app/views/shared/_clone_panel.html.haml

@@ -2,7 +2,7 @@
 
 .git-clone-holder.js-git-clone-holder.input-group
   .input-group-prepend
-    - if allowed_protocols_present? && project.visibility_level == Gitlab::VisibilityLevel::PUBLIC || (current_user && !current_user.cas_user?)
+    - if allowed_protocols_present? && @project.visibility_level == Gitlab::VisibilityLevel::PUBLIC || (current_user && !current_user.cas_user?)
       .input-group-text.clone-dropdown-btn.btn
         %span.js-clone-dropdown-label
           = enabled_project_button(project, enabled_protocol)
@@ -14,7 +14,7 @@
       %ul.dropdown-menu.dropdown-menu-selectable.clone-options-dropdown
         %li
           = ssh_clone_button(project)
-        - if project.visibility_level == Gitlab::VisibilityLevel::PUBLIC || (current_user && !current_user.cas_user?)
+        - if @project.visibility_level == Gitlab::VisibilityLevel::PUBLIC || (current_user && !current_user.cas_user?)
           %li
             = http_clone_button(project)