Without knowing what column you are primarily sorting because you have not said, let's say it is column B.
The cells are NOT blank as they contain "" (empty text). Use a hidden column to sort by in your sort criteria. Example:
=IF(B1="","ZZZZ",B1) where Column "B" houses your formulas. "Z" is the last alphanumeric character in the hierarchy chain, and four Z's should ensure the returned value is not like any other bona fide value.