fix(array3d_export): loop over array shape to fix case for disu grid

flopy/export/utils.py

@@ -1207,7 +1207,7 @@ def array3d_export(f: Union[str, os.PathLike], u3d, fmt=None, **kwargs):
         f
     ).suffix.lower() == ".shp":
         array_dict = {}
-        for ilay in range(modelgrid.nlay):
+        for ilay in range(u3d.array.shape[0]):
             u2d = u3d[ilay]
             if isinstance(u2d, np.ndarray):
                 dname = u3d.name