Fix rendering of SVGs in Add Content shortcuts

Steps to Reproduce:

• In Studio, Create two new document types, Cheese and Contract
• Add the relevant SVG images as their icons (use attached SVGs).
• Hot reload the customizations to Nuxeo.
• Create one of each doc type.
• Hover on the Add Content button.
  => Cheese doc type icon displays in beautiful monochrome contrast.
  => Contract doc type icon displays as white circle.

Expected behavior:

• All SVG icons should be displayed in blue/white contrast.
  OR
• Maybe mention a warning if certain icons with white won't render well.