Do not use len() without comparison to determine if a sequence is empty

Author: DimitriPapadopoulos

xarray/computation/fit.py

@@ -474,7 +474,7 @@ def _wrapper(Y, *args, **kwargs):
             mask = np.all([np.any(~np.isnan(x), axis=0), ~np.isnan(y)], axis=0)
             x = x[:, mask]
             y = y[mask]
-            if not len(y):
+            if y.size == 0:
                 popt = np.full([n_params], np.nan)
                 pcov = np.full([n_params, n_params], np.nan)
                 return popt, pcov