BUG: None / Timedelta incorrectly returning NaT
- [ ] closes #xxxx
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

xref #31869, arguable whether or not this closes that.
Not against the design just curious as to what your thought is as to why this should raise instead of returning NaN? Perhaps because np.nan / pd.NaT is ambiguous? > why this should raise instead of returning NaN? Perhaps because np.nan / pd.NaT is ambiguous?

Think of it as if we had non-NA scalars of the same types/dtypes.  e.g. `2.0 / Timedelta(days=1)` is obviously gibberish.  So treat `np.nan / Timedelta(days=1)` the same thanks