Issue is shown here. This is most likely a compatibility issue with AppleSkin, which is the mod that adds the food info tooltips. Either way, definitely worth investigating due to how commonly the AppleSkin mod is used.

I would fix if I could but I am using the villager trading GUI, not a custom GUI. Problems lies more with AppleSkin.

Can you test this with a villager with custom trades? It's possible the issue hasn't been seen before because Villagers by default don't accept food as a buy item. If this is an issue, please create an issue on AppleSkin and reference this thread.
/summon villager ~ ~1 ~ {VillagerData:{profession:farmer,level:2,type:plains},Offers:{Recipes:[{buy:{id:apple,Count:1},sell:{id:apple,Count:1},rewardExp:0b,maxUses:9999999}]}}

Okay, so I tested myself. No issues...

Hrm, did you have OptiFine installed as well during your test?

There's your problem

Regardless of the issue, nothing I can do because I simply use the Villager trade GUI. Follow up with the AppleSkin dev.

Another commands for Villager with more trades if you need to test if the issue happens with villagers too.
/summon villager ~ ~1 ~ {VillagerData:{profession:farmer,level:2,type:plains},Offers:{Recipes:[{buy:{id:apple,Count:1},sell:{id:apple,Count:1},rewardExp:0b,maxUses:9999999},{buy:{id:bread,Count:1},sell:{id:bread,Count:1},rewardExp:0b,maxUses:9999999}]}}

Ah yep, happening with villagers as well. I'll notify the AppleSkin dev.