Where column a is a quantity and column e is a dollar amount and column F is the result of a and e multiplied I get a #value error if any of the rows are empty(which some will be empty)

for example in
in cell f46 I want the result of A46 x e46 and in cell F100 I want the sum of f46..f 99) but if any of the cells in the f column are blank because no quantity in the A column entered I get #value error. I don't want the users to have to put zeros in all the a column fields that they don't enter a quantity.