Open URL does not validate URL scheme; fails silently.

[bennie]

Attempting to open a URL that is not of a supported Open-URL scheme fails silently to the UI.

Examples:

  nfs://192.168.1.20/foo.txt
  gopher://192.168.1.20/foo.txt
  rsync://192.168.1.20/foo.txt

The debug trace implies it is being handled as a file open:

  No such file or directory when trying to open 'nfs://192.168.1.23/foo.txt' at /Users/phil/Documents/work/padre/Padre/lib/Padre/Wx/Main.pm line 4095.