Simple calculation error performing (A*B)+(C*D)+(E*F) with blank cells

[Kilian]

Found a simple calculation error performing (AxB)+(CxD)+(ExF) with blank cells.

(AB)+(CD) or (CD)+(EF) handle blank cells as expected but chaining three (AB)+(CD)+(EF) or more (AB)+(CD)+(EF)+(H*I) together throws a wobbly!