Combined account balance fixes needed for unit tests

src/main/java/org/qortal/account/Account.java

@@ -77,6 +77,12 @@ public class Account {
 			throw new DataException(message);
 		}
 
+		// Delete account balance record instead of setting balance to zero
+		if (balance.signum() == 0) {
+			this.repository.getAccountRepository().delete(this.address, assetId);
+			return;
+		}
+
 		// Can't have a balance without an account - make sure it exists!
 		this.repository.getAccountRepository().ensureAccount(this.buildAccountData());
 

src/main/java/org/qortal/payment/Payment.java

@@ -250,8 +250,10 @@ public class Payment {
 			 * For QORT amounts only: If recipient's last reference is this transaction's signature, then they can't have made any transactions of their own
 			 * (which would have changed their last reference) thus this is their first reference so remove it.
 			 */
-			if ((alwaysUninitializeRecipientReference || assetId == Asset.QORT) && Arrays.equals(recipient.getLastReference(), signature))
+			if ((alwaysUninitializeRecipientReference || assetId == Asset.QORT) && Arrays.equals(recipient.getLastReference(), signature)) {
 				recipient.setLastReference(null);
+				this.repository.getAccountRepository().delete(recipient.getAddress(), assetId);
+			}
 		}
 	}
 

src/main/java/org/qortal/repository/hsqldb/HSQLDBAssetRepository.java

@@ -188,6 +188,9 @@ public class HSQLDBAssetRepository implements AssetRepository {
 	public void delete(long assetId) throws DataException {
 		try {
 			this.repository.delete("Assets", "asset_id = ?", assetId);
+
+			// Also delete account balances that refer to asset
+			this.repository.delete("AccountBalances", "asset_id = ?", assetId);
 		} catch (SQLException e) {
 			throw new DataException("Unable to delete asset from repository", e);
 		}