The changes in commit a2e2825 broke pot recipes that don't use any item ingredients (as a consequence of fixing jam canning recipes, since the commit made the output provider only take non-empty inputs from the pot). Since this kind of pot recipe may exist in addons (i.e. Cottage Cheese in Kuba's TFC Additions), this should get fixed.

Since this isn't really solvable when confined to just the SimplePotRecipe type as it stands (at least not without breaking canning recipes again, judging from a cursory glance at the code), perhaps a new recipe type should be added for this?