Delete keychain item if radar password is cleared
Delete keychain item if radar password is cleared

Clearing out the radar password in preferences currently does
nothing—this commit deletes the password item from the user’s keychain
if one already exists.

Inferis/QuickRadar,JanX2/QuickRadar,amyworrall/QuickRadar,phatblat/QuickRadar,johankj/QuickRadar