fix: handle missing 'weight' attribute in edge data to prevent KeyError

- Add validation in _find_most_related_edges_from_entities and  _get_edge_data function during edge data construction
- Add warning logs when 'weight' attribute is missing and set default value of 0.0

lightrag/operate.py

@@ -1609,6 +1609,10 @@ async def _find_most_related_edges_from_entities(
     for pair in all_edges:
         edge_props = edge_data_dict.get(pair)
         if edge_props is not None:
+            if "weight" not in edge_props:
+                logger.warning(f"Edge {pair} missing 'weight' attribute, using default value 0.0")
+                edge_props["weight"] = 0.0
+                
             combined = {
                 "src_tgt": pair,
                 "rank": edge_degrees_dict.get(pair, 0),
@@ -1670,6 +1674,10 @@ async def _get_edge_data(
         pair = (k["src_id"], k["tgt_id"])
         edge_props = edge_data_dict.get(pair)
         if edge_props is not None:
+            if "weight" not in edge_props:
+                logger.warning(f"Edge {pair} missing 'weight' attribute, using default value 0.0")
+                edge_props["weight"] = 0.0
+                
             # Use edge degree from the batch as rank.
             combined = {
                 "src_id": k["src_id"],