RepoBrowser: Bring back "open with" and "open with alternative editor" for selected files

Fix regression of ce98fe882ba3fffbc394ae0c2fae2173f0f43fae and c6c8d224a7d3040e8e7aebd72e12216a040ab818

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>