ffcae82a68104c1992964b26c592b62cbca391bf test: exercise TransactionMerklePath with empty block; targets the MerkleComputation empty-leaves path that was only reached by fuzz tests (frankomosh)
Pull request description:
As noted in [#32243 (comment)](https://github.com/bitcoin/bitcoin/pull/32243#issuecomment-2988854482), the early return inside `MerkleComputation` when `leaves.size() == 0` was only exercised by fuzz tests.
The existing `merkle_test_empty_block` calls `BlockMerkleRoot`, which uses `ComputeMerkleRoot`, but does not exercise the `TransactionMerklePath` → `ComputeMerklePath` → `MerkleComputation` code path.
Coverage before adding test:
<img width="2459" height="66" alt="before" src="https://github.com/user-attachments/assets/ca94015a-d7c2-4281-ac60-13b22f177b67" />
Coverage after adding test:
<img width="2459" height="66" alt="after" src="https://github.com/user-attachments/assets/b1d4e1bb-af72-46ab-8898-f18db39dd2fb" />
ACKs for top commit:
kevkevinpal:
ACK [ffcae82](ffcae82a68)
maflcko:
lgtm ACK ffcae82a68104c1992964b26c592b62cbca391bf
brunoerg:
code review ACK ffcae82a68104c1992964b26c592b62cbca391bf
sedited:
ACK ffcae82a68104c1992964b26c592b62cbca391bf
Tree-SHA512: d2499d91269c4f4f9a86011f7ad13f675834662a5bd37b0e7cbe887a7d9acf4170e53f0bdc528011fc82866b9c1dec34f4e7e9cd64cc3100591c1580a4df5d00
b8e66b901d