null is also an object, so check against that first

Changelog.md

@@ -2,6 +2,10 @@
 
 All notable changes to this project will be documented in this file.
 
+
+## [0.94] - 2025-03-19
+- Fix Excel export for data that includes null values
+
 ## [0.93] - 2025-03-03
 - Fix CSV/Excel export for data that includes object/array values
 

compendium-frontend/src/components/download/DownloadDataButton.tsx

@@ -11,6 +11,7 @@ interface DownloadProps {
 }
 
 function simplifyObjectOrArray(obj) {
+    if (obj == null) return obj
     if (Array.isArray(obj)) {
         return obj.map(simplifyObjectOrArray).join(', ');
     }