Reproduce by changing the furnace from electric to steel/stone then reloading webpage. The furnace icon will be a black box (because of line 156). The steel/stone furnace will not be used in any calculations (because of line 145).
Fix:
settings.js, line 144
furnace = settings.furnace should be furnace = {name: settings.furnace}or (but I prefer the one above)
the two furnace.names on lines 145 & 156 could be just furnace
Reproduce by changing the furnace from electric to steel/stone then reloading webpage. The furnace icon will be a black box (because of line 156). The steel/stone furnace will not be used in any calculations (because of line 145).
Fix: settings.js, line 144
furnace = settings.furnace
should befurnace = {name: settings.furnace}
or (but I prefer the one above) the twofurnace.names
on lines 145 & 156 could be justfurnace