Exit program on vector index creation failure for MongoDB

lightrag/kg/mongo_impl.py

@@ -1419,7 +1419,9 @@ class MongoVectorDBStorage(BaseVectorStorage):
             logger.info(f"Vector index {self._index_name} created successfully.")
 
         except PyMongoError as e:
-            logger.error(f"Error creating vector index {self._index_name}: {e}")
+            error_msg = f"Error creating vector index {self._index_name}: {e}"
+            logger.error(error_msg)
+            raise SystemExit(f"Failed to create MongoDB vector index. Program cannot continue. {error_msg}")
 
     async def upsert(self, data: dict[str, dict[str, Any]]) -> None:
         logger.debug(f"Inserting {len(data)} to {self.namespace}")