Do not use IF(ISBLANK(A1),"",A1). That works only when A1 is truly empty,
i.e. it has no formula and no constant. But as you can with the result in
B2, your perception of a cell with "no data" might be misled by a formula
that results in the null string.
Of course, if you truly want to distinguish between the null string and
truly empty -- very rare -- ISBLANK() is indeed the function to use.