have table where I need to summ numbers from cells with letters beside numbers

A1=ED2, A2=ED1, A3=ED1, A4=ED4, A5=RE2...

have formula =SUMPRODUCT(--RIGHT(E3:I3;1)) which is ok if there is no empty cell in the range, result is 10.

can someone help to find right formula if cell A2 is empty ?

thx