Fix 1515 (#1516)

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### Pull Request Checklist:
- [x] This PR addresses an already opened issue (for bug fixes /
features)
    - This PR fixes #1515 
- [ ] Tests for the changes have been added (for bug fixes / features)
- [ ] (If applicable) Documentation has been added / updated (for bug
fixes / features)
- [x] CHANGES.rst has been updated (with summary of main changes)
- [ ] Link to issue (:issue:`number`) and pull request (:pull:`number`)
has been added

### What kind of change does this PR introduce?

* fixes issue #1515 

### Does this PR introduce a breaking change?


### Other information:

CHANGES.rst

@@ -2,6 +2,14 @@
 Changelog
 =========
 
+v0.47.0 (unreleased)
+--------------------
+Contributors to this version: Juliette Lavoie (:user:`juliettelavoie`)
+
+Bug fixes
+^^^^^^^^^
+* Fixed a bug with ``n_escore=-1`` in ``xclim.sdba.adjustment.NpdfTransform`` (:issue:`1515`, :pull:`1515`).
+
 v0.46.0 (2023-10-24)
 --------------------
 Contributors to this version: David Huard (:user:`huard`), Trevor James Smith (:user:`Zeitsperre`), Pascal Bourgault (:user:`aulemahal`), Éric Dupuis (:user:`coxipi`).

xclim/sdba/_adjustment.py

@@ -309,7 +309,7 @@ def npdf_transform(ds: xr.Dataset, **kwargs) -> xr.Dataset:
         # All NaN, but with the proper shape.
         escores = (
             ref.isel({dim: 0, "time": 0}) * hist.isel({dim: 0, "time": 0})
-        ).expand_dims(iterations=ds.iteration) * np.NaN
+        ).expand_dims(iterations=ds.iterations) * np.NaN
 
     return xr.Dataset(
         data_vars={