Search bugs in all projects fails with an UnexpectedFormData error

Steps to reproduce (using sample data):
1. http://bugs.launchpad.dev/
2. In the search field enter 'foo';
3. Select 'All projects' and click 'Search bug reports';
4. You're redirected to http://bugs.launchpad.dev/bugs/+bugs?field.searchtext=foo&search=Search+Bug+Reports&field.scope=all&field.scope.target=
5. Now enter 'foo bar' in the search field and click search;
6. An UnexpectedFormData is raised. OOPS-428BC175

Module canonical.widgets.project, line 98, in getInputValue
    raise UnexpectedFormData("No valid option was selected.")
UnexpectedFormData: No valid option was selected.

Step 5 to 6 should be similar to step 3 to 4, instead of raising raising an UFD.