Null or 0 returns on formula errors.

I have the following formula in a form that I use to track machine output (the formula was created with the formula wizard.)

=INDEX('C:\My Documents\[Formulas.xls]price matrix'!$A$1:$H$100, MATCH(J7,'C:\My Documents\[Formulas.xls]price matrix'!$A$1:$A$100,), MATCH(I7,'C:\My Documents\[Formulas.xls]price matrix'!$A$1:$H$1,))

The template also does further calculations on the results of this formula. But the formula as written returns #N/A as a result if either J7 or I7 is null (no entry.) How can I edit this so that it returns a 0 (zero) value, if J7 or I7 is empty?