From e9f20ef085715472ad03c6ac1605b7a4fd265aab Mon Sep 17 00:00:00 2001
From: AlexanderSinn <alexander.sinn@desy.de>
Date: Tue, 21 May 2024 17:14:39 +0200
Subject: [PATCH] Fix openPMD crash if beam has no particles

---
 src/diagnostics/OpenPMDWriter.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/diagnostics/OpenPMDWriter.cpp b/src/diagnostics/OpenPMDWriter.cpp
index 4f91f039d8..71c052aad7 100644
--- a/src/diagnostics/OpenPMDWriter.cpp
+++ b/src/diagnostics/OpenPMDWriter.cpp
@@ -245,6 +245,12 @@ OpenPMDWriter::WriteBeamParticleData (MultiBeam& beams, openPMD::Iteration itera
         SetupPos(beam_species, beam, np_total, geom);
         SetupRealProperties(beam_species, real_names, np_total);
 
+        if (np_total == 0) {
+            amrex::ErrorStream() << "WARNING: Beam '" << name
+                                 << "' has no particles! No output will be written.\n";
+            continue;
+        }
+
         for (std::size_t idx=0; idx<m_uint64_beam_data[ibeam].size(); idx++) {
             uint64_t * const uint64_data = m_uint64_beam_data[ibeam][idx].get();