Backup before NAT cancel fix

src/etcp_api.c

@@ -114,6 +114,11 @@ int etcp_send(struct ETCP_CONN* conn, struct ll_entry* entry) {
         DEBUG_ERROR(DEBUG_CATEGORY_ETCP_API, "etcp_send: Connection has no normalizer");
         return -1;
     }
+    if (conn->initialized==0) {
+        DEBUG_ERROR(DEBUG_CATEGORY_ETCP_API, "etcp_send: Connection is not initialized");
+        return -1;
+    }
+
     struct PKTNORM* pn = conn->normalizer;
     if (!pn || !pn->input) {
         DEBUG_ERROR(DEBUG_CATEGORY_ETCP_API, "etcp_send: pn=%p or input null", pn);