refactor(node_evaluators): Move the empty list handling to the base c…

…lass

syntheseus/search/node_evaluation/base.py

@@ -75,6 +75,9 @@ def num_calls(self) -> int:
     def __call__(
         self, nodes: Sequence[NodeType], graph: Optional[RetrosynthesisSearchGraph] = None
     ) -> Sequence[float]:
+        if not nodes:  # handle the case when there are no nodes to score
+            return []
+
         self._num_calls += len(nodes)
         return self._evaluate_nodes(nodes, graph)
 
@@ -138,9 +141,6 @@ def _get_probability(self, node, graph) -> float:
         return metadata["probability"]  # type: ignore
 
     def _evaluate_nodes(self, nodes, graph=None) -> Sequence[float]:
-        if not nodes:  # handle the case when there are no nodes to score
-            return []
-
         probs = np.asarray([self._get_probability(n, graph) for n in nodes])
         probs = np.clip(probs, a_min=self._clip_probability_min, a_max=self._clip_probability_max)