To reproduce:
1. Go to Control Panel, Configuration, Instance Settings, Miscellaneous, Display Settings
2. Configure any language other than English as Default Language
3. Logout
4. Login
5. Activate local staging
Actual result:
javax.portlet.PortletException: java.lang.NullPointerException
full trace is here: https://gist.github.com/kmaria/3ae688cc59894375cb3635f5cc89c226
Expected:
local staging to be enabled
Tested on ee-7.0.x 311f4b8