00/01/1900 in excel has the value of 0, you can see this by typing this date into a number formatted cell.
If you simply equate the result of your formula against one then you can just return a blank cell instead:
=IF([YOUR FORMULA]=0,"",[YOUR FORMULA])
Or if you know it will return 00.01.1900 every time this occurs then you could substitute that text out of the cell:
=SUBSTITUTE([YOUR FORMULA],"00.01.1900","")
