Empty cell filling in Excel.

Select The Range where data needs to fill in blank cell.

Press F5 or Ctrl+G - Special - Blank

          ( F5 or Ctrl+G will open Go To window then There will be Special option in the left bottom corner of the Go To window, click on that then there will be a list of option, where you need to select Blank option which is in 4th option in left option list.)

Then use following method to fill first cell of blank selection and press Ctrl+Enter.  

As you will press Ctrl+Enter all blank cell will be filled as there upper cell. Like following image.

Then select complete range and copy and paste special as value only.