refactor(diagram): improve null handling and update dependencies

- Add null checks in edge and node constructors to prevent runtime errors
- Use optional chaining to improve code readability and robustness
- Update Vite to version 3.2.11
- Add 'exports: "named"' to vite config for better module resolution

package.json

@@ -98,7 +98,7 @@
     "terser-webpack-plugin": "^3.1.0",
     "ts-node": "^10.9.1",
     "typescript": "^4.9.4",
-    "vite": "^3.2.10",
+    "vite": "^3.2.11",
     "vite-plugin-css-injected-by-js": "^2.2.0",
     "vite-svg-loader": "^4.0.0",
     "vitest": "^0.26.1"