You were given a string of integer temperature values. Create a function `lowest_temp(t)` and return the lowest value or `None/null/Nothing` if the string is empty.
def lowest_temp(t):
    if t:
        return min([int(x) for x in t.split()])
    else:
        return None

def lowest_temp(t):
    if t:
        return min([int(x) for x in t.split()])
    else:
        return None
