From 03e911d5e434eecd1a17a8dee8bc20940d4b12c2 Mon Sep 17 00:00:00 2001
From: Lukas Holik <kiloh.sakul@gmail.com>
Date: Thu, 28 Sep 2023 14:15:37 +0200
Subject: [PATCH] tf's review

---
 src/nfa/intersection.cc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/nfa/intersection.cc b/src/nfa/intersection.cc
index bc79d79c8..55426026b 100644
--- a/src/nfa/intersection.cc
+++ b/src/nfa/intersection.cc
@@ -40,6 +40,9 @@ Nfa intersection(const Nfa& lhs, const Nfa& rhs, const Symbol first_epsilon, Pro
         return lhs.final.contains(lhs_state) && rhs.final.contains(rhs_state);
     };
 
+    if (lhs.final.empty() || lhs.initial.empty() || rhs.initial.empty() || rhs.final.empty())
+        return Nfa{};
+
     return algorithms::product(lhs, rhs, both_final, first_epsilon, prod_map);
 }