credit handling fix

Author: Petr Matousek

src/api/qpid-proton/reactor/handler/TxReceiverHandler.cpp

@@ -138,11 +138,13 @@ void TxReceiverHandler::on_session_open(session &s) {
         s.transaction_declare(*this);
     } else {
         logger(trace) << "[on_session_open] Transaction is declared: " << s.transaction_id();
+        if (count != 0 && (processed + batch_size > count)) {
+           batch_size = count % batch_size;
+        } else if (count == 0) {
+            batch_size = 1;
+        }
         recv.add_credit(batch_size);
         logger(debug) << "[on_session_open] Receiver credit: " << recv.credit();
-        if (count != 0 && processed + batch_size > count) {
-            batch_size = count % batch_size;
-	}
     }
 }