From aaf92a1a946cf4c52edf7f40b30fe970a168bccb Mon Sep 17 00:00:00 2001
From: Anton Alkin <anton.alkin@cern.ch>
Date: Tue, 23 Apr 2024 08:27:14 +0200
Subject: [PATCH] PWGMM: ambiguous track propagation: prevent crash in corner
 cases

---
 PWGMM/Mult/TableProducer/trackPropagation.cxx | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/PWGMM/Mult/TableProducer/trackPropagation.cxx b/PWGMM/Mult/TableProducer/trackPropagation.cxx
index 678759a211f..314bc59a2b2 100644
--- a/PWGMM/Mult/TableProducer/trackPropagation.cxx
+++ b/PWGMM/Mult/TableProducer/trackPropagation.cxx
@@ -129,10 +129,13 @@ struct AmbiguousTrackPropagation {
   using ExTracksSel = soa::Join<aod::Tracks, aod::TracksExtra, aod::TrackSelection, aod::TracksDCA, aod::TrackCompColls>;
 
   void processCentral(ExTracksSel const& tracks,
-                      aod::Collisions const& collisions,
-                      ExtBCs const&)
+                      aod::Collisions const&,
+                      ExtBCs const& bcs)
   {
-    auto bc = collisions.begin().bc_as<ExtBCs>();
+    if (bcs.size() == 0) {
+      return;
+    }
+    auto bc = bcs.begin();
     initCCDB(bc);
 
     gpu::gpustd::array<float, 2> dcaInfo;