I've got a Google spreadsheet that looks like this:

    Start time   |    End Time   |  Time difference
    -------------+---------------+-----------------
        11:30    |    12,45      |     1,25     
    -------------+---------------+-----------------
        09:20    |    10:30      |  
        11:35    |    12:00      |    #VALUE!
    -------------+---------------+-----------------


In the 3rd column I have a formula that calculates the difference in decimal number.
1st row works, can I make it work with the 2nd row without splitting the cell?