# scikit-learn__scikit-learn-13779
# Loki Mode Multi-Agent Patch
# Attempts: 1

Based on my knowledge of the scikit-learn codebase and the issue described, I'll generate the patch. The bug occurs because in the `fit` method, the code checks for `sample_weight` support on all estimators before filtering out `None` ones. The fix is to filter out `None` estimators before doing the `sample_weight` support check.

--- a/sklearn/ensemble/voting.py
+++ b/sklearn/ensemble/voting.py
@@ -78,7 +78,7 @@ class _BaseVoting(TransformerMixin, _BaseHeterogeneousEnsemble):
 
         if sample_weight is not None:
             for name, step in self.estimators:
-                if not has_fit_parameter(step, 'sample_weight'):
+                if step is not None and not has_fit_parameter(step, 'sample_weight'):
                     raise ValueError('Underlying estimator \'%s\' does not'
                                      ' support sample weights.' % name)