In Dropbutton, do not show links that the user does not have access to

I came across this using Commerce.
Occasionally, an order gets locked (e.g. after payment gateway errors).
On the cart views, there is a drop button with actions to perform on every cart.

When a cart is locked, it's not possible to access the "modify" link on the drop button, and the anchors text remains empty.
That throws an Undefined array key "title" in template_preprocess_links() warning for every locked cart.

The MR removes the link and prevents warnings.

• I've tested the MR 2561.
• Apply the patch
• Create a page view for content. Select 'Table' display
• Add 'Custom text' field to the view and add the following