Fix: prevent SQL errors when metadata filter Constant value is None or blank (#21803)

api/core/rag/retrieval/dataset_retrieval.py

     def _process_metadata_filter_func(
         self, sequence: int, condition: str, metadata_name: str, value: Optional[Any], filters: list
     ):
+        if value is None:
+            return
+
         key = f"{metadata_name}_{sequence}"
         key_value = f"{metadata_name}_{sequence}_value"
         match condition:

api/core/workflow/nodes/knowledge_retrieval/knowledge_retrieval_node.py

     def _process_metadata_filter_func(
         self, sequence: int, condition: str, metadata_name: str, value: Optional[Any], filters: list
     ):
+        if value is None:
+            return
+
         key = f"{metadata_name}_{sequence}"
         key_value = f"{metadata_name}_{sequence}_value"
         match condition: