Fix null case for sygus printing (#4793)

Avoids crashing on some of our debug traces.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/theory/quantifiers/sygus/term_database_sygus.cpp b/src/theory/quantifiers/sygus/term_database_sygus.cpp
index ff1b172e9..ac10522a2 100644
--- a/src/theory/quantifiers/sygus/term_database_sygus.cpp
+++ b/src/theory/quantifiers/sygus/term_database_sygus.cpp
@@ -731,6 +731,11 @@ void TermDbSygus::toStreamSygus(const char* c, Node n)
 
 void TermDbSygus::toStreamSygus(std::ostream& out, Node n)
 {
+  if (n.isNull())
+  {
+    out << n;
+    return;
+  }
   // use external conversion
   out << datatypes::utils::sygusToBuiltin(n, true);
 }