Currency converter: Fix crash when system uses unsupported locale

Close #950

data/currencies/src/main/java/de/mm20/launcher2/currencies/CurrencyRepository.kt

@@ -15,8 +15,16 @@ class CurrencyRepository(
     private val context: Context,
 ) {
 
+    private fun getOwnCurrency(): String {
+        return try {
+            java.util.Currency.getInstance(Locale.getDefault()).currencyCode ?: "USD"
+        } catch (e: IllegalArgumentException) {
+            "USD"
+        }
+    }
+
     private val currencySymbolAliases = buildMap {
-        val ownCurrency = java.util.Currency.getInstance(Locale.getDefault()).currencyCode ?: "USD"
+        val ownCurrency = getOwnCurrency()
 
         put("€", "EUR")