fix: handle 0n as from/to blocks in getContractEvents (#4919)

Fixes CNCT-1987

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---

## PR-Codex overview
This PR focuses on improving the validation of `fromBlock` and `toBlock` parameters in the `getContractEvents` function to ensure they are explicitly defined before performing any calculations.

### Detailed summary
- Updated condition to check if `fromBlock` and `toBlock` are not `undefined` instead of truthy.
- Adjusted logic for setting `restParams.toBlock` and `restParams.fromBlock` based on the new checks.

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Author: joaquim-verges

.changeset/heavy-camels-help.md

@@ -0,0 +1,5 @@
+---
+"thirdweb": patch
+---
+
+Fix passing 0n as from/to blocks in getContractEvents

packages/thirdweb/src/event/actions/get-events.ts

@@ -124,18 +124,18 @@ export async function getContractEvents<
 
     // Make sure the inputs were properly defined
     if (
-      fromBlock &&
-      toBlock &&
+      fromBlock !== undefined &&
+      toBlock !== undefined &&
       BigInt(toBlock) - BigInt(fromBlock) !== BigInt(blockRange)
     ) {
       throw new Error(
         "Incompatible blockRange with specified fromBlock and toBlock. Please only define fromBlock or toBlock when specifying blockRange.",
       );
     }
 
-    if (fromBlock) {
+    if (fromBlock !== undefined) {
       restParams.toBlock = BigInt(fromBlock) + BigInt(blockRange) - 1n; // Subtract one because toBlock is inclusive
-    } else if (toBlock) {
+    } else if (toBlock !== undefined) {
       restParams.fromBlock = BigInt(toBlock) - BigInt(blockRange) + 1n; // Add one because fromBlock is inclusive
     } else {
       // If no from or to block specified, use the latest block as the to block