Hide issues and MRs in labels list if disabled

What does this MR do?

Hide view issues and merge requests from labels list if the project has issues or merge request disabled.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

The links lead to an error page if the features were disabled for the project.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

app/views/shared/_label.html.haml

@@ -11,12 +11,14 @@
       = icon('caret-down')
     .dropdown-menu.dropdown-menu-align-right
       %ul
-        %li
-          = link_to_label(label, subject: subject, type: :merge_request) do
-            view merge requests
-        %li
-          = link_to_label(label, subject: subject) do
-            view open issues
+        - if !(defined?(@project) && label.is_a?(ProjectLabel) && !@project.merge_requests_enabled?)
+          %li
+            = link_to_label(label, subject: subject, type: :merge_request) do
+              view merge requests
+        - if !(defined?(@project) && label.is_a?(ProjectLabel) && !@project.issues_enabled?)
+          %li
+            = link_to_label(label, subject: subject) do
+              view open issues
         - if current_user && defined?(@project)
           %li.label-subscription
             - if label.is_a?(ProjectLabel)
@@ -37,10 +39,12 @@
             = link_to 'Delete', destroy_label_path(label), title: 'Delete', method: :delete, data: {confirm: 'Remove this label? Are you sure?'}
   .pull-right.hidden-xs.hidden-sm.hidden-md
-    = link_to_label(label, subject: subject, type: :merge_request, css_class: 'btn btn-transparent btn-action') do
-      view merge requests
-    = link_to_label(label, subject: subject, css_class: 'btn btn-transparent btn-action') do
-      view open issues
+    - if !(defined?(@project) && label.is_a?(ProjectLabel) && !@project.merge_requests_enabled?)
+      = link_to_label(label, subject: subject, type: :merge_request, css_class: 'btn btn-transparent btn-action') do
+        view merge requests
+    - if !(defined?(@project) && label.is_a?(ProjectLabel) && !@project.issues_enabled?)
+      = link_to_label(label, subject: subject, css_class: 'btn btn-transparent btn-action') do
+        view open issues
     - if current_user && defined?(@project)
       .label-subscription.inline
@@ -82,4 +86,4 @@
         new gl.ProjectLabelSubscription('##{dom_id(label)} .label-subscription');
     - else
       :javascript
-        new gl.GroupLabelSubscription('##{dom_id(label)} .label-subscription');
+        new gl.GroupLabelSubscription('##{dom_id(label)} .label-subscription');
\ No newline at end of file