TokenSign was copying unused Arena held by Standalone instead of refering to it.
An Arena has to be used at least once before it holds a valid, copyable reference.
Otherwise the lifecycle of the copied Arena would be its own and not be shared with the original.
Thus, when the copied arena went out of scope,
the memory supposed to be held by returned Standalone also got released.
Fix: instead of copying, refer to Standalone's arena.
Junhyun Shim