[iOS] Zero out NSError to avoid heap corruptions for the OSS builds (#65355)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/65355
I've been seeing heap corruptions in the CMake builds due to the NSError* not being initialized with `nil`. However, I haven't see this issue for the BUCK builds.
ghstack-source-id: 138502708
Test Plan:
1. Test the OSS builds to make sure the heap corruption has gone.
2. Test the Buck build in the playground app
3. Circle CI
Reviewed By: hanton
Differential Revision: D31048010
fbshipit-source-id: cfd8d614f3f91f09caee4aab61237007ec080481
