From 285b835a02f7beac506df5588400a3990a234408 Mon Sep 17 00:00:00 2001
From: swenzel <sandro.wenzel@cern.ch>
Date: Tue, 28 Jan 2025 14:37:14 +0100
Subject: [PATCH] DigitizationContext: Prevent a segfault in QED filling

---
 DataFormats/simulation/src/DigitizationContext.cxx | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/DataFormats/simulation/src/DigitizationContext.cxx b/DataFormats/simulation/src/DigitizationContext.cxx
index 975458c41fcb3..e875cb61951a9 100644
--- a/DataFormats/simulation/src/DigitizationContext.cxx
+++ b/DataFormats/simulation/src/DigitizationContext.cxx
@@ -289,6 +289,11 @@ DigitizationContext* DigitizationContext::loadFromFile(std::string_view filename
 
 void DigitizationContext::fillQED(std::string_view QEDprefix, int max_events, double qedrate)
 {
+  if (mEventRecords.size() <= 1) {
+    // nothing to do
+    return;
+  }
+
   o2::steer::InteractionSampler qedInteractionSampler;
   qedInteractionSampler.setBunchFilling(mBCFilling);