NaN headers lead to issues in some steps

[naterush]

          1. Create this dataframe

import pandas as pd
df = pd.DataFrame({'A': [None, 1, 2], 'B': [None,1,3]})

2. Promote the first row to the header
3. Add a column and set the formula =nan (1)1, and see that it works
4. Add a column and set the formula =nan1, and see that it errors

https://user-images.githubusercontent.com/18709905/234399483-b8056eea-6a8e-40c2-9a9e-fa99684c5627.mov

EDIT: there are going to be nan issues across the codebase with nan columns. I think it's an improvement for now, and I haven't see anyone trying to do other things with them. Going to just open a bug and leave this for now.

Originally posted by @aarondr77 in https://github.com/mito-ds/monorepo/issues/724#issuecomment-1522394630