cryptonote: fix reuse of non default tx data when relaying

An automatic tx variable is initialized properly on the first
run through the loop, but not the second. Moving the variable
inside the loop ensures the ctor is called again to init it.

src/cryptonote_basic/cryptonote_format_utils.cpp

@@ -146,6 +146,8 @@ namespace cryptonote
     if (tx.version >= 2 && !is_coinbase(tx))
     {
       rct::rctSig &rv = tx.rct_signatures;
+      if (rv.type == rct::RCTTypeNull)
+        return true;
       if (rv.outPk.size() != tx.vout.size())
       {
         LOG_PRINT_L1("Failed to parse transaction from blob, bad outPk size in tx " << get_transaction_hash(tx));