fix lag when opening currencies fragment

app/src/main/java/net/pokeranalytics/android/ui/fragment/CurrenciesFragment.kt

@@ -44,15 +44,19 @@ class CurrenciesFragment : PokerAnalyticsFragment(), StaticRowRepresentableDataS
 			)
 		}
 
+        private val availableCurrencyLocales = Locale.getAvailableLocales().mapNotNull {
+            try {
+                Currency.getInstance(it)
+            } catch (e: Exception) {
+                null
+            }
+        }
+
 		private val availableCurrencies = this.systemCurrencies.filter {
 			!mostUsedCurrencyCodes.contains(it.currencyCode)
 		}.filter {
-			Locale.getAvailableLocales().filter { locale ->
-				try {
-					Currency.getInstance(locale).currencyCode == it.currencyCode
-				} catch (e: Exception) {
-					false
-				}
+			availableCurrencyLocales.filter { currencyLocale ->
+                currencyLocale.currencyCode == it.currencyCode
 			}.isNotEmpty()
 		}.sortedBy {
 			it.displayName