From dee4b7425ccc814f8d882c8e73048646545eb6b1 Mon Sep 17 00:00:00 2001
From: Fabian Zills <46721498+PythonFZ@users.noreply.github.com>
Date: Thu, 21 Dec 2023 11:32:34 +0100
Subject: [PATCH] fix IndexError

---
 znh5md/znh5md/h5ase.py | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/znh5md/znh5md/h5ase.py b/znh5md/znh5md/h5ase.py
index edfb161..a87bfe4 100644
--- a/znh5md/znh5md/h5ase.py
+++ b/znh5md/znh5md/h5ase.py
@@ -17,11 +17,15 @@ def _gather_value(particles_data, key, idx):
 
     Returns None if the key is not present in the data.
     """
-    if key in particles_data:
-        if key in [GRP.species, GRP.position, GRP.velocity, GRP.forces, GRP.momentum]:
-            # use PARTICLES_GRP
-            return rm_nan(particles_data[key][idx])
-        return particles_data[key][idx]
+    try:
+        if key in particles_data:
+            if key in [GRP.species, GRP.position, GRP.velocity, GRP.forces, GRP.momentum]:
+                # use PARTICLES_GRP
+                return rm_nan(particles_data[key][idx])
+            return particles_data[key][idx]
+    except IndexError:
+        # a property might not be available at all frames.
+        pass
     return None