TIDDIT output folder named `null`

[apeltzer]

As described on SLack, the output folder of the current dev branch for TIDDIT when annotated is simply called null.

[asp8200]

@FriederikeHanssen : Are you solving this issue or should I take a look at it?

[maxulysse]

It'll be fixed by #618

[FriederikeHanssen]

#618 is merged