Optimize empty check for BinaryData (#889)

Updated the condition to check if `partitionContent` is empty by using
the `IsEmpty` property instead of converting it to a byte array and
checking its length. This change improves efficiency and readability.

service/Core/Handlers/TextPartitioningHandler.cs

@@ -120,7 +120,7 @@ public TextPartitioningHandler(
                 string partitionsMimeType = MimeTypes.PlainText;
 
                 // Skip empty partitions. Also: partitionContent.ToString() throws an exception if there are no bytes.
-                if (partitionContent.ToArray().Length == 0) { continue; }
+                if (partitionContent.IsEmpty) { continue; }
 
                 switch (file.MimeType)
                 {