community[patch]: clean warning when delete by ids (#19301)

* Description: rearrange to avoid variable overwrite, which cause
warning always.
* Issue: N/A
* Dependencies: N/A

libs/community/langchain_community/vectorstores/milvus.py

@@ -933,11 +933,11 @@ class Milvus(VectorStore):
             kwargs: Other parameters in Milvus delete api.
         """
         if isinstance(ids, list) and len(ids) > 0:
-            expr = f"{self._primary_field} in {ids}"
             if expr is not None:
                 logger.warning(
                     "Both ids and expr are provided. " "Ignore expr and delete by ids."
                 )
+            expr = f"{self._primary_field} in {ids}"
         else:
             assert isinstance(
                 expr, str