Set default auth mode to prevent double popup (#4274)

## Problem solved

Short description of the bug fixed or feature added

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---

## PR-Codex overview
This PR fixes a conflict between popup and window authentication modes on Firefox.

### Detailed summary
- Set the default authentication mode to "popup" if not specified
- Ensure popup authentication mode is used when not explicitly defined

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.changeset/tame-badgers-drum.md

@@ -0,0 +1,5 @@
+---
+"thirdweb": patch
+---
+
+Fix popup and window auth modes conflicting on firefox

packages/thirdweb/src/wallets/in-app/core/wallet/index.ts

@@ -40,7 +40,9 @@ export async function connectInAppWallet(
   connector: InAppConnector,
 ): Promise<[Account, Chain]> {
   if (
+    // if auth mode is not specified, the default is popup
     createOptions?.auth?.mode !== "popup" &&
+    createOptions?.auth?.mode !== undefined &&
     connector.authenticateWithRedirect
   ) {
     const strategy = options.strategy;