Here’s some basic instructions to select and clear these blank cells to make them blank:

  1. Press ctrl + a or pre-select your range.
  2. Press ctrl + f.
  3. Leave find what empty and select match entire cell contents.
  4. Hit find all.
  5. Press ctrl + a to select all the empty cells found.
  6. Close the find dialog.
  7. Press backspace or delete.

Source: Excel telling me my blank cells aren’t blank – Stack Overflow