From c732750c76726301d0418166dcf84629952b0315 Mon Sep 17 00:00:00 2001
From: Chris Markiewicz <effigies@gmail.com>
Date: Wed, 16 Aug 2023 10:11:55 -0400
Subject: [PATCH] FIX: Drop JSON sidecar fields with null values during
 metadata indexing

---
 bids/layout/index.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/bids/layout/index.py b/bids/layout/index.py
index 62cbec26..38800d0e 100644
--- a/bids/layout/index.py
+++ b/bids/layout/index.py
@@ -465,6 +465,10 @@ def create_association_pair(src, dst, kind, kind2=None):
 
             # Create Tag <-> Entity mappings, and any newly discovered Entities
             for md_key, md_val in file_md.items():
+                # Treat null entries (deserialized to None) as absent
+                # Alternative is to cast None to null in layout.models._create_tag_dict
+                if md_val is None:
+                    continue
                 tag_string = '{}_{}'.format(bf.path, md_key)
                 # Skip pairs that were already found in the filenames
                 if tag_string in all_tags: