The svg icons included in notmuch-emacs cannot be correctly rendered
by emacs-mac (https://bitbucket.org/mituharu/emacs-mac/src/master/),
which uses OSX's builtin frameworks instead of imagemagick to render
images.

The empty SVG created by `svg-image' function from svg.el has XML
attribute `xmlns' like:

"<svg width=\"50\" height=\"50\" version=\"1.1\" xmlns=\"http://www.w3.org/2000/svg\" xmlns:xlink=\"http://www.w3.org/1999/xlink\">
</svg>"

which is missing from SVG icons defined in `notmuch-tag.el'

Thanks.

--
LDB