Revert "s/.done(/.then(/ since modern es6 track unhandled promise exceptions"

This reverts commit 09a8fec2

src/components/views/elements/ImageView.js

@@ -84,7 +84,7 @@ export default class ImageView extends React.Component {
                         title: _t('Error'),
                         description: _t('You cannot delete this image. (%(code)s)', {code: code}),
                     });
-                }).then();
+                }).done();
             },
         });
     };