Fix test failing due to assuming a different default locale

TransactionTest.testCreateAutoBalanceSplit assumed a default locale with
EUR commodity. The default commodity is set in new Transaction objects,
which might change depending on the environment where the tests are run.
Now we set it explicitly in the tests.

app/src/test/java/org/gnucash/android/test/unit/model/TransactionTest.java

@@ -80,6 +80,7 @@ public void settingUID_shouldSetTransactionUidOfSplits(){
 	@Test
 	public void testCreateAutoBalanceSplit() {
 		Transaction transactionCredit = new Transaction("Transaction with more credit");
+        transactionCredit.setCommodity(Commodity.getInstance("EUR"));
 		Split creditSplit = new Split(new Money("1", "EUR"), "test-account");
 		creditSplit.setType(TransactionType.CREDIT);
 		transactionCredit.addSplit(creditSplit);
@@ -93,6 +94,7 @@ public void testCreateAutoBalanceSplit() {
 
 
 		Transaction transactionDebit = new Transaction("Transaction with more debit");
+		transactionDebit.setCommodity(Commodity.getInstance("EUR"));
 		Split debitSplit = new Split(new Money("1", "EUR"), "test-account");
 		debitSplit.setType(TransactionType.DEBIT);
 		transactionDebit.addSplit(debitSplit);