#46752: Fix missing offset assignment logic in checkpoint store

Author: kamil-di

sdk/eventhubs/azure-messaging-eventhubs-checkpointstore-blob/src/main/java/com/azure/messaging/eventhubs/checkpointstore/blob/BlobCheckpointStore.java

@@ -258,7 +258,15 @@ public Mono<Void> updateCheckpoint(Checkpoint checkpoint) {
         Map<String, String> metadata = new HashMap<>();
         String sequenceNumber
             = checkpoint.getSequenceNumber() == null ? null : String.valueOf(checkpoint.getSequenceNumber());
-
+        
+        String offset;
+        if (checkpoint.getOffsetString() == null || checkpoint.getOffsetString().isEmpty()) {
+            offset = String.valueOf(checkpoint.getOffset());
+        } else {
+            offset = checkpoint.getOffsetString();
+        }
+        metadata.put(SEQUENCE_NUMBER, sequenceNumber);
+        metadata.put(OFFSET, offset);
         metadata.put(SEQUENCE_NUMBER, sequenceNumber);
         metadata.put(OFFSET, checkpoint.getOffsetString());
         BlobAsyncClient blobAsyncClient = blobClients.get(blobName);