Print crash record optionally

src/net.c

@@ -300,6 +300,9 @@ void mg_mgr_free(struct mg_mgr *mgr) {
   mgr->timers = NULL;  // Important. Next call to poll won't touch timers
   for (c = mgr->conns; c != NULL; c = c->next) c->is_closing = 1;
   mg_mgr_poll(mgr, 0);
+#if MG_ENABLE_MDASH
+  mg_mdash_free(mgr);
+#endif
 #if MG_ENABLE_FREERTOS_TCP
   FreeRTOS_DeleteSocketSet(mgr->ss);
 #endif