cell display does not change

Hello everyone

I have a formula which equates integers to quartertone-pitches.
My problem: if the cell designed for number-input is empty, the cell with the pitch-name displays B≠ (b-quarter-sharp).
Please see the attached file: rows 1 and 2 are normal; row 9 demonstrates the problem.

I would need the cell to be empty (or display "0" or "value") if there is no number inputted.
How can I change that without altering the rest of the formula?

Thank you in advance for your advice.