fix: should always contain gas price info even if it's 0 (#5673)

https://linear.app/thirdweb/issue/CNCT-2602/issue-signing-deploy-tx-on-saakura

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## PR-Codex overview
This PR focuses on ensuring that gas price information is always included for enclave wallets, even when it is 0. It modifies the condition for setting the `maxFeePerGas` to check for the type `bigint`.

### Detailed summary
- Updated the condition to check if `tx.maxFeePerGas` is of type `bigint`.
- Ensured that `transaction.maxFeePerGas` is set correctly when `tx.maxFeePerGas` is provided.

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Author: ElasticBottle

.changeset/nervous-pots-smell.md

@@ -0,0 +1,5 @@
+---
+"thirdweb": patch
+---
+
+always include gas price information even if it's 0 for enclave wallets

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

@@ -162,7 +162,7 @@ export class EnclaveWallet implements IWebWallet {
         chainId: toHex(tx.chainId),
       };
 
-      if (tx.maxFeePerGas) {
+      if (typeof tx.maxFeePerGas === "bigint") {
         transaction.maxFeePerGas = toHex(tx.maxFeePerGas);
         transaction.maxPriorityFeePerGas =
           typeof tx.maxPriorityFeePerGas === "bigint"