wallet: use optional for change position as an optional in CreateTransaction

Instead of making -1 a magic number meaning no change or random change
position, use an optional to have that meaning.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/wallet/interfaces.cpp b/src/wallet/interfaces.cpp
index 4ca5e29229..d15273dfc9 100644
--- a/src/wallet/interfaces.cpp
+++ b/src/wallet/interfaces.cpp
@@ -281,12 +281,12 @@ public:
         CAmount& fee) override
     {
         LOCK(m_wallet->cs_wallet);
-        auto res = CreateTransaction(*m_wallet, recipients, change_pos,
+        auto res = CreateTransaction(*m_wallet, recipients, change_pos == -1 ? std::nullopt : std::make_optional(change_pos),
                                      coin_control, sign);
         if (!res) return util::Error{util::ErrorString(res)};
         const auto& txr = *res;
         fee = txr.fee;
-        change_pos = txr.change_pos;
+        change_pos = txr.change_pos ? *txr.change_pos : -1;
 
         return txr.tx;
     }