fix a bug in kwant.qsymm
We were adding an empty dictionary to a Model, which is not an API and worked by accident previously.
I also bump the qsymm requirement to 1.2.4, but am unsure if we are allowed to do this between patch releases of Kwant.
We were adding an empty dictionary to a Model, which is not an API and worked by accident previously.
I also bump the qsymm requirement to 1.2.4, but am unsure if we are allowed to do this between patch releases of Kwant.