Why is my Food Advisor telling me my "Catnip supply is too low"?

It's an estimate based off a "normal" winter (-75% catnip production). The script calculates the current catnip production and tells you if you will last winter with it. I say "estimate" because the math assumes winter just started.

The game operates in ticks. There are 10 ticks in one day, so it woild be 10 * catnipPerTick per one day, 0-100 days per winter.

For reference, here is the related source code:

updateAdvisors: function(){

    if (this.bld.get("field").val == 0){
        return;
    }

    var advDiv = dojo.byId("advisorsContainer");
    dojo.empty(advDiv);

    var winterDays = 100;
    if (this.calendar.season == "winter"){
        winterDays = 100 - this.calendar.day;
    }

    var catnipPerTick = this.getResourcePerTick("catnip", false, { modifiers:{
        "catnip" : 0.25
    }});    //calculate estimate winter per tick for catnip;

    if (this.resPool.get("catnip").value + ( winterDays * catnipPerTick * 10 ) <= 0 ){
        advDiv.innerHTML = "<span>Food advisor: 'Your catnip supply is too low!'<span>"
    }

}

The warning is triggered when your catnip supplies are low enough to reach 0 if your production goes in negative values (cold winter for example).
If your catnip production is in positive values at all times, even at the lowest possible happiness levels, then you shouldn't be getting this warning even when you use up all your catnip.