Format: don't call toString() blindly
Format: don't call toString() blindly

Instead, use String() as a function. It fixes passing null or
undefined to format().

https://bugzilla.gnome.org/show_bug.cgi?id=687153

pixunil/cjs,pixunil/cjs,endlessm/gjs,endlessm/gjs,djdeath/gjs,pixunil/cjs,endlessm/gjs,mtwebster/cjs,djdeath/gjs,mtwebster/cjs,pixunil/cjs,djdeath/gjs,endlessm/gjs,endlessm/gjs,djdeath/gjs,mtwebster/cjs,mtwebster/cjs,pixunil/cjs,mtwebster/cjs,djdeath/gjs