Need help using ISERROR with Index/Match function

I am using the following formula:

=INDEX('April wk 1'!$C$15:$C$300,MATCH(1,($A5='April wk 1'!$A$15:$A$300)*($B5='April wk 1'!$B$15:$B$300),0))

I am using this to pull the number of units shipped to a particular store(in column A on both spreadsheets) and of a particular item(in column B on both spreadsheets)

The formula is working perfectly except if it cannot find both criteria, an #n/a error returns(instead of a 0). I need to be able to sum the data so would like to use something to either return a blank, or a 0. Any help would be greatly appreciated.

Thanks!!!