Wallet: Ensure m_attaching_chain is set before registering for signals

Avoids a race where chainStateFlushed could be called before rescanning began, yet rescan gets interrupted or fails

Author: luke-jr

src/wallet/wallet.cpp

@@ -2961,6 +2961,7 @@ bool CWallet::AttachChain(const std::shared_ptr<CWallet>& walletInstance, interf
     // so that in case of a shutdown event, the rescan will be repeated at the next start.
     // This is temporary until rescan and notifications delivery are unified under same
     // interface.
+    walletInstance->m_attaching_chain = true; //ignores chainStateFlushed notifications
     walletInstance->m_chain_notifications_handler = walletInstance->chain().handleNotifications(walletInstance);
 
     // If rescan_required = true, rescan_height remains equal to 0
@@ -2987,7 +2988,6 @@ bool CWallet::AttachChain(const std::shared_ptr<CWallet>& walletInstance, interf
 
     if (tip_height && *tip_height != rescan_height)
     {
-        walletInstance->m_attaching_chain = true; //ignores chainStateFlushed notifications
         if (chain.havePruned()) {
             int block_height = *tip_height;
             while (block_height > 0 && chain.haveBlockOnDisk(block_height - 1) && rescan_height != block_height) {
@@ -3031,6 +3031,7 @@ bool CWallet::AttachChain(const std::shared_ptr<CWallet>& walletInstance, interf
         walletInstance->chainStateFlushed(chain.getTipLocator());
         walletInstance->GetDatabase().IncrementUpdateCounter();
     }
+    walletInstance->m_attaching_chain = false;
 
     return true;
 }