Fix "locale" container parameter
Fix "locale" container parameter

The "locale" parameter is an artefact of the default configuration of Symfony Standard Edition, but there is no guarantee that it is defined. In case it's not defined, we should fallback to `kernel.default_locale` which is defined by FrameworkBundle.
OskarStark/EasyAdminBundle,OskarStark/EasyAdminBundle,javiereguiluz/EasyAdminBundle,yceruto/EasyAdminBundle,OskarStark/EasyAdminBundle,yceruto/EasyAdminBundle,javiereguiluz/EasyAdminBundle,yceruto/EasyAdminBundle