Important FIX to payment-related isValid()!

Non-native-coin payments (e.g. transfer-asset) didn't build map
for checking whether sender had enough balance.

Also fixed raw layout description for TRANSFER_ASSET.

Also fixed ISSUE_ASSET deserialization to use empty string (instead
of null) for v1 transactions.

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

@@ -79,7 +79,7 @@ public class Payment {
 				return ValidationResult.INVALID_AMOUNT;
 
 			// Set or add amount into amounts-by-asset map
-			amountsByAssetId.compute(paymentData.getAssetId(), (assetId, amount) -> amount == null ? amount : amount.add(paymentData.getAmount()));
+			amountsByAssetId.compute(paymentData.getAssetId(), (assetId, amount) -> amount == null ? paymentData.getAmount() : amount.add(paymentData.getAmount()));
 		}
 
 		// Check sender has enough of each asset

src/main/java/org/qora/transform/transaction/IssueAssetTransactionTransformer.java

@@ -76,7 +76,7 @@ public class IssueAssetTransactionTransformer extends TransactionTransformer {
 		boolean isDivisible = byteBuffer.get() != 0;
 
 		// in v2, assets have "data" field
-		String data = null;
+		String data = "";
 		if (timestamp >= BlockChain.getInstance().getQoraV2Timestamp())
 			data = Serialization.deserializeSizedString(byteBuffer, Asset.MAX_DATA_SIZE);
 

src/main/java/org/qora/transform/transaction/TransferAssetTransactionTransformer.java

@@ -32,7 +32,7 @@ public class TransferAssetTransactionTransformer extends TransactionTransformer
 		layout.add("transaction's groupID", TransformationType.INT);
 		layout.add("reference", TransformationType.SIGNATURE);
 		layout.add("asset owner's public key", TransformationType.PUBLIC_KEY);
-		layout.add("asset's new owner", TransformationType.ADDRESS);
+		layout.add("asset quantity", TransformationType.ASSET_QUANTITY);
 		layout.add("asset ID", TransformationType.LONG);
 		layout.add("fee", TransformationType.AMOUNT);
 		layout.add("signature", TransformationType.SIGNATURE);