./CorsixTH/Lua/dialogs/fullscreen/research_policy.lua:113: attempt to call field 'gfind' (a nil value)

stack traceback:

        ./CorsixTH/Lua/dialogs/fullscreen/research_policy.lua:113: in function 'get_localized_string'

        ./CorsixTH/Lua/dialogs/fullscreen/research_policy.lua:123: in function 'updateCategories'

        ./CorsixTH/Lua/dialogs/fullscreen/research_policy.lua:67: in function 'constructor'

        ./CorsixTH/Lua/class.lua:76: in function '?'

        ./CorsixTH/Lua/dialogs/bottom_panel.lua:733: in function 'addDialog'

        ./CorsixTH/Lua/dialogs/bottom_panel.lua:621: in function 'callback'

        ./CorsixTH/Lua/window.lua:664: in function 'handleClick'

        ./CorsixTH/Lua/window.lua:1439: in function 'onMouseUp'

        ./CorsixTH/Lua/window.lua:1423: in function 'onMouseUp'

        ./CorsixTH/Lua/ui.lua:622: in function <./CorsixTH/Lua/ui.lua:609>

        (...tail calls...)

        ./CorsixTH/Lua/app.lua:768: in function <./CorsixTH/Lua/app.lua:763>