DeltaDebugger#ddmin does not minimize to empty input

[TheSilvus]

The minimization implementation does not minimize as I would expect if all inputs cause the failure:

def asdf(s):
    assert False
with DeltaDebugger() as dd:
    asdf("test")
print(dd)

[andreas-zeller]

Thanks! The difference between passing input (here: the empty string) and failing input is normally non-empty, but I have added a check for the case that the empty string already fails (which makes sense as it also discovers internal errors). This is now fixed in the latest git version.