fix: default currency in case of no currency

Author: aggarwalpulkit596

app/src/main/java/org/fossasia/openevent/general/event/EventDetailsFragment.kt

@@ -192,7 +192,9 @@ class EventDetailsFragment : Fragment() {
             rootView.organizerContainer.isVisible = false
         }
 
-        currency = Currency.getInstance(event.paymentCurrency).symbol
+        event.paymentCurrency.let {
+            currency = Currency.getInstance(it ?: "USD").symbol
+        }
         // About event on-click
         val aboutEventOnClickListener = View.OnClickListener {
             AboutEventFragmentArgs.Builder()