flipdna() breaks visualizeflow()

[abs-yy]

Hi @ponnhide,
The flipdna() function against a QUEEN instance breaks visualizeflow(). Here's a minimal example.

This works without any errors (No flow map would be visualized though).

M13F = QUEEN("GTAAAACGACGGCCAGT")
visualizeflow(M13F)

However, this one fails with the error below.

M13F = QUEEN("GTAAAACGACGGCCAGT")
visualizeflow(flipdna(M13F))

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[83], line 1
----> 1 visualizeflow(flipdna(M13F))

File ~/micromamba/envs/general/lib/python3.11/site-packages/QUEEN/qgraph.py:845, in visualizeflow(search_function, grouping, inherited_process, process_description, split_input, sf, ip, pd, si, alias_dict, *dnas)
    843 sdgflag = 0 
    844 for productname in productnames:
--> 845     if "_load" in info_dict and "cutdna" not in funcname:
    846         if productname not in nodes:
    847             dg.node(productname, label=productname, margin="0.05", shape="oval", fontname="Arial") 

TypeError: argument of type 'NoneType' is not iterable

Here's my environment

% pip list | grep -i queen
python-queen                  1.2.0