fix: resolve Gateway depositor address in payout burn path

depositorWallet was declared but never assigned, so every payout that
reached the Gateway execution path (auto-mode fallback and user-selected
cross-chain) threw 'Cannot read properties of undefined' at the burn
call and surfaced as a generic 500.

Replace it with a hoisted depositorAddress that is assigned in both
routing branches: the selected wallet's address in wallet mode, and the
EOA found holding the Gateway balance in auto mode. Guard the burn call
so an unresolved depositor returns an explicit error instead of a crash.

Author: theyavuzarslan

app/api/payout/route.ts

@@ -134,7 +134,7 @@ export const POST = withAuth(async (req, { user, supabase }) => {
 
     // Routing logic based on source type
     let sourceWallet: WalletBalance | undefined;
-    let depositorWallet: typeof wallets[0] | undefined; // Wallet that has the Gateway balance
+    let depositorAddress: Address | undefined; // EOA that holds the Gateway balance (burn source)
     let strategy: "same-chain" | "gateway" = "same-chain";
     let estimatedFee = 0.50;
     let estimatedTime = 30;
@@ -174,6 +174,8 @@ export const POST = withAuth(async (req, { user, supabase }) => {
         estimatedFee = 2.01;
         estimatedTime = 60;
         useGateway = true;
+        // The selected wallet is the EOA whose Gateway balance will be burned
+        depositorAddress = selectedWallet.address as Address;
       }
 
       console.log(`User selected wallet: ${sourceWallet.walletId} on ${sourceWallet.chain}`);
@@ -545,6 +547,7 @@ export const POST = withAuth(async (req, { user, supabase }) => {
         strategy = "gateway";
         estimatedFee = 2.01;
         estimatedTime = 60;
+        depositorAddress = eoaAddressWithBalance;
         console.log(`Auto-selected Gateway from ${bestSourceChain}. Balance: ${Number(maxGatewayBalance) / 1_000_000} USDC from EOA ${eoaAddressWithBalance}`);
       }
     }
@@ -558,14 +561,25 @@ export const POST = withAuth(async (req, { user, supabase }) => {
       console.log(`Initiating Gateway transfer from ${sourceWallet.chain} to ${destinationChain}`);
 
       // Step 1: Burn with EOA signature
-      // Use the depositor wallet address (the one that has the Gateway balance)
+      // Use the depositor address (the EOA that holds the Gateway balance)
+      if (!depositorAddress) {
+        return NextResponse.json(
+          {
+            error: "No Gateway depositor address resolved",
+            userMessage:
+              "Could not determine which wallet holds the Gateway balance for this transfer. Please retry or select a source wallet explicitly.",
+          },
+          { status: 500 }
+        );
+      }
+
       const { transferId, attestation, attestationSignature } = await signAndSubmitGatewayBurnIntent(
         user.id,
         amountInAtomicUnits,
         sourceWallet.chain,
         destinationChain,
         recipientAddress as Address,
-        depositorWallet.address as Address // Pass the depositor address
+        depositorAddress // Pass the depositor address
       );
 
       console.log(`Burn intent submitted. Transfer ID: ${transferId}`);