[backport#13546] wallet: Fix use of uninitialized value bnb_used in C…

…Wallet::CreateTransaction(...)

Summary:
wallet: Avoid potential use of unitialized value bnb_used in CWallet::CreateTransaction(...) (practicalswift)

Pull request description:

  Avoid use of uninitialized value `bnb_used` in `CWallet::CreateTransaction(...)`.

bitcoin/bitcoin@a23a7f6

---

Backport of Core [[bitcoin/bitcoin#13546 | PR13546]]

Test Plan:
  ninja check check-functional

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D7060

src/wallet/wallet.cpp

@@ -3461,6 +3461,8 @@ bool CWallet::CreateTransaction(interfaces::Chain::Lock &locked_chainIn,
                         return false;
                     }
                 }
+            } else {
+                bnb_used = false;
             }
 
             const Amount nChange = nValueIn - nValueToSelect;