smtp: don't create transaction for trailing quit

Ticket: OISF#8728

Author: jasonish

src/app-layer-smtp.c

@@ -1280,8 +1280,9 @@ static int SMTPProcessRequest(
     if (line->len == 0 && line->delim_len == 0) {
         return 0;
     }
-    if (state->curr_tx == NULL ||
-            (SMTPTransactionRequestIsComplete(state->curr_tx) && !NoNewTx(state, line))) {
+    const bool no_new_tx = NoNewTx(state, line);
+    if ((state->curr_tx == NULL && !no_new_tx) ||
+            (SMTPTransactionRequestIsComplete(state->curr_tx) && !no_new_tx)) {
         tx = SMTPTransactionCreate(state);
         if (tx == NULL)
             return -1;
@@ -1297,7 +1298,9 @@ static int SMTPProcessRequest(
     if (frame != NULL && state->curr_tx) {
         AppLayerFrameSetTxId(frame, state->curr_tx->tx_id);
     }
-    tx->tx_data.updated_ts = true;
+    if (tx != NULL) {
+        tx->tx_data.updated_ts = true;
+    }
 
     state->toserver_data_count += (line->len + line->delim_len);