Fix -Wmissing-braces warning in clang
Fix -Wmissing-braces warning in clang

peterdettman/secp256k1,bitcoin-core/secp256k1,ElementsProject/secp256k1-zkp,bitcoin/secp256k1,bitcoin/secp256k1,bitcoin/secp256k1,bitcoin/secp256k1,peterdettman/secp256k1,ElementsProject/secp256k1-zkp,bitcoin-core/secp256k1,bitcoin/secp256k1