Update lib/histogram.js

Co-authored-by: Simen Bekkhus <[email protected]>

Author: Dan Shappir

lib/histogram.js

@@ -290,7 +290,7 @@ function extractBucketValuesForExport(histogram) {
 				{ le: upperBound },
 				acc,
 				name,
-				(bucketExemplars && bucketExemplars[upperBound]) || null,
+				bucketExemplars?.[upperBound] ?? null,
 				labels,
 			);
 		});