fix various build issues

web/src/components/events/EventDetails.tsx

@@ -11,7 +11,7 @@ function formatPrice(price: number | string): string {
   }
   const asNumber = Number(price);
   if (isNaN(asNumber)) {
-    return price;
+    return price.toString();
   }
   if (asNumber === 0) {
     return "Gratis";

web/src/components/venues/VenueItem.tsx

@@ -9,9 +9,9 @@ export const VenueItem = ({ venue }: { venue: VenueFragment }) => {
   const { capacitySitting, capacityStanding, usedFor } = venue;
   let capacity = null;
   if (
-    !isNaN(capacitySitting) &&
+    !isNaN(Number(capacitySitting)) &&
     capacitySitting &&
-    !isNaN(capacityStanding) &&
+    !isNaN(Number(capacityStanding)) &&
     capacityStanding
   ) {
     capacity = `${capacitySitting}—${capacityStanding}`;