Fix: Prevent Undefined nodes and edges in GraphCreator Initialization

[ByeongUkChoi]

Summary

This PR ensures that nodes and edges properties in GraphCreator are always initialized as arrays, preventing potential undefined errors when processing uploaded files.

Changes

• Updated CypherController.js:
  • Set nodes and edges to default to empty arrays ([]) if req.files.nodes or req.files.edges are undefined.

Reason for Change

• If req.files.nodes or req.files.edges is missing, GraphCreator would receive undefined, potentially causing runtime errors during graph parsing.
• Defaulting these values to empty arrays ensures that downstream operations, such as map() and forEach(), do not fail.

Impact

• Improves robustness when handling file uploads.
• Prevents potential crashes due to missing properties.
• Ensures GraphCreator always has valid nodes and edges arrays to work with.