…acks

- Fixed serializeLocalTransformation to handle nil nodes gracefully
- Changed transform array from optional to non-optional Float array
- Changed node name from optional to non-optional String
- Store node reference before clearing panningNode to prevent nil access
- Only invoke onPanEnd/onRotationEnd if node exists

This fixes the issue where call.arguments["name"] was nil, causing
the Dart callback handler to fail silently in the catch block.

- Added defensive null check for name before creating transformMap
- Only invoke callback if name exists (consistent with iOS fix)
- Prevents potential crashes when name is null from nodeData["name"]