fix(message): Fixed bug in final length calculation in Multipart Encoded

Previously, footerLength was added as many times as the number of contents, but we changed it to adding it only once at the end.

src/message.js

@@ -149,11 +149,13 @@ function multipartEncode(
     const contentArray = new Uint8Array(datasetBuffer);
     const contentLength = contentArray.length;
 
-    length += headerLength + contentLength + footerLength;
+    length += headerLength + contentLength
 
     return contentArray;
   });
 
+  length += footerLength;
+
   // Allocate the array
   const multipartArray = new Uint8Array(length);