chore: improve readability

Author: RobbyUitbeijerse

packages/thirdweb/src/react/web/ui/ConnectWallet/screens/Buy/fiat/FiatScreenContent.tsx

@@ -87,14 +87,14 @@ export function FiatScreenContent(props: {
       : undefined,
   );
 
-  const supportedProviders =
-    buyWithFiatOptions !== false
-      ? !!buyWithFiatOptions?.supportedProviders?.length &&
-        (!preferredProvider ||
-          buyWithFiatOptions.supportedProviders.includes(preferredProvider))
-        ? buyWithFiatOptions?.supportedProviders
-        : [...FiatProviders]
-      : [];
+  const supportedProviders = (() => {
+    if (!buyWithFiatOptions) return [];
+    const options = buyWithFiatOptions?.supportedProviders ?? [];
+    return options.length > 0 &&
+      (!preferredProvider || options.includes(preferredProvider))
+      ? options
+      : [...FiatProviders];
+  })();
 
   const fiatQuoteQuery = useBuyWithFiatQuote(
     buyWithFiatOptions !== false && tokenAmount