From 24603cd82c201f913833ca9a5f455648437e8357 Mon Sep 17 00:00:00 2001
From: aferrero2707 <aferrero1975@gmail.com>
Date: Mon, 19 Jan 2026 18:30:06 +0100
Subject: [PATCH] [PWGDQ] bugfix in matching QA task

Fixed crash when the collision table is empty
---
 PWGDQ/Tasks/qaMatching.cxx | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/PWGDQ/Tasks/qaMatching.cxx b/PWGDQ/Tasks/qaMatching.cxx
index 9b5cdef037c..9ba6c2dd1c0 100644
--- a/PWGDQ/Tasks/qaMatching.cxx
+++ b/PWGDQ/Tasks/qaMatching.cxx
@@ -1773,6 +1773,9 @@ struct qaMatching {
       collisionIds.push_back(collision.globalIndex());
     }
 
+    if (collisionIds.empty())
+      return;
+
     for (size_t cid = 1; cid < collisionIds.size() - 1; cid++) {
       const auto& collision = collisions.rawIteratorAt(collisionIds[cid]);
       int64_t collisionIndex = collision.globalIndex();