validate bib sorting choices
validate bib sorting choices

fixes failure to update the sorting submenu when the URL is something
like #/bib/ (in which case major === "")

joncgoodwin/dfr-browser,joncgoodwin/dfr-browser,joncgoodwin/dfr-browser,agoldst/dfr-browser,joncgoodwin/dfr-browser,altaf-ali/dfr-browser,altaf-ali/dfr-browser,altaf-ali/dfr-browser,agoldst/dfr-browser,joncgoodwin/dfr-browser,altaf-ali/dfr-browser,agoldst/dfr-browser,agoldst/dfr-browser