guard for fiat amount being null

lib/new-ui/pages/buy_sell/buy_sell_provider_page.dart

@@ -135,7 +135,9 @@ class _BuySellProviderPageState extends State<BuySellProviderPage> {
       " " +
       (widget.buySellViewModel.cryptoCurrency.fullName ?? "");
 
-  ListItem quoteListItem(Quote quote) => ListItemRegularRow(
+  ListItem quoteListItem(Quote quote) {
+    final fiatAmount = widget.buySellViewModel.fiatAmountForQuote(quote);
+    return ListItemRegularRow(
       keyValue: quote.provider.title,
       label: quote.rampName ?? quote.provider.title,
       secondaryLabel: quote.rampName != null ? quote.provider.title : null,
@@ -155,11 +157,13 @@ class _BuySellProviderPageState extends State<BuySellProviderPage> {
           Text(widget.buySellViewModel
               .amountForQuote(quote)
               .toStringWithSymbol(fractionalDigits: 8)),
+          if(fiatAmount != null)
           Text(
-              "= ${widget.buySellViewModel.fiatAmountForQuote(quote).toStringWithSymbol(fractionalDigits: 2, trimZeros: false)}",
+              "= ${fiatAmount.toStringWithSymbol(fractionalDigits: 2, trimZeros: false)}",
               style: TextStyle(fontSize: 12, color: Theme.of(context).colorScheme.onSurfaceVariant))
         ],
       ));
+  }
 
   void navigateToConfirmation(BuildContext context) {
     final page = BuySellConfirmationPage(buySellViewModel: widget.buySellViewModel);

lib/view_model/buy/buy_sell_view_model.dart

@@ -175,11 +175,18 @@ abstract class BuySellViewModelBase extends WalletChangeListenerViewModel with S
       (double.parse(fiatAmount) / quote.rate).toStringAsFixed(cryptoCurrency.decimals),
       cryptoCurrency);
 
-  Money fiatAmountForQuote(Quote quote) => Money.safeParse(
+  @computed
+  Money? fiatAmountForQuote(Quote quote) {
+    if(fiatConversionStore.prices[cryptoCurrency] == null) {
+      return null;
+    }
+
+    return Money.safeParse(
         (fiatConversionStore.prices[cryptoCurrency]! *
                 double.parse(amountForQuote(quote).toString()))
             .toStringAsFixed(2),
         fiatCurrency);
+  }
 
   // based on usd values, should have roughly equal worth (was done with ai though so it's subject to correction)
   static final Map<FiatCurrency, List<String>> _defaultAmountsMap = {