Fix get single node subgrap problem

- Replaced MATCH with OPTIONAL MATCH
- Add memory-bank directory for Cline to .gitignore

.gitignore

@@ -64,3 +64,9 @@ gui/
 
 # unit-test files
 test_*
+
+# Cline files
+memory-bank/
+
+# Cline files
+memory-bank/

lightrag/kg/neo4j_impl.py

@@ -661,7 +661,7 @@ class Neo4JStorage(BaseGraphStorage):
                     WITH collect({node: n}) AS filtered_nodes
                     UNWIND filtered_nodes AS node_info
                     WITH collect(node_info.node) AS kept_nodes, filtered_nodes
-                    MATCH (a)-[r]-(b)
+                    OPTIONAL MATCH (a)-[r]-(b)
                     WHERE a IN kept_nodes AND b IN kept_nodes
                     RETURN filtered_nodes AS node_info,
                            collect(DISTINCT r) AS relationships
@@ -704,7 +704,7 @@ class Neo4JStorage(BaseGraphStorage):
                     WITH collect({node: node}) AS filtered_nodes
                     UNWIND filtered_nodes AS node_info
                     WITH collect(node_info.node) AS kept_nodes, filtered_nodes
-                    MATCH (a)-[r]-(b)
+                    OPTIONAL MATCH (a)-[r]-(b)
                     WHERE a IN kept_nodes AND b IN kept_nodes
                     RETURN filtered_nodes AS node_info,
                            collect(DISTINCT r) AS relationships