From bcdd2a82a0154f8c406dadd451e61c08a27c7b34 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ji=C5=99=C3=AD=20Locker?= <jiri.locker@gmail.com>
Date: Fri, 17 May 2024 00:39:43 +0200
Subject: [PATCH] Avoid IndexOutOfBoundsException in lhsUnary

---
 .../java/org/drools/drl/parser/antlr4/DRLVisitorImpl.java    | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drools-drl/drools-drl-parser/src/main/java/org/drools/drl/parser/antlr4/DRLVisitorImpl.java b/drools-drl/drools-drl-parser/src/main/java/org/drools/drl/parser/antlr4/DRLVisitorImpl.java
index 7001beed648..485928d6e7a 100644
--- a/drools-drl/drools-drl-parser/src/main/java/org/drools/drl/parser/antlr4/DRLVisitorImpl.java
+++ b/drools-drl/drools-drl-parser/src/main/java/org/drools/drl/parser/antlr4/DRLVisitorImpl.java
@@ -1087,9 +1087,10 @@ public BaseDescr visitLhsUnary(DRLParser.LhsUnaryContext ctx) {
                     .build();
             children.forEach(andDescr::addDescr);
             return andDescr;
-        } else {
-            // size == 1. children never be empty
+        } else if (children.size() == 1) {
             return children.get(0);
+        } else {
+            return null; // only caused by a parser error
         }
     }