IFERROR(VLOOKUP) That returns "0" when reference cell is empty

Hopefully this should be easy for someone. Posted an example, see cell J3 on sheet1 for what comes through. Reference data is on sheet2.

This is the formula =IFERROR(VLOOKUP($A3,sheet2!$A$3:$L$3,J1,FALSE),"") and it keeps returning a "0" (zero) when the reference cell is blank.

I've gone to the reference cells and hit delete just to make sure there is nothing in them but 0 still comes through. I've tried to reformat all the cells too but that doesn't work.
Thoughts?