Fix chain bug

Author: lnbc1QWFyb24

packages/core/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@web3-onboard/core",
-  "version": "2.0.0-alpha.5",
+  "version": "2.0.0-alpha.6",
   "scripts": {
     "build": "rollup -c",
     "dev": "rollup -c -w",

packages/core/src/provider.ts

@@ -266,6 +266,9 @@ export async function getBalance(
   address: string,
   chain: Chain
 ): Promise<Balances | null> {
+  // chain we don't recognize
+  if (!chain) return null
+
   if (!ethersProviders[chain.rpcUrl]) {
     ethersProviders[chain.rpcUrl] = new providers.StaticJsonRpcProvider(
       chain.rpcUrl