security: plug memory leaks in transform

refs #3758

Change-Id: Id8e3aa33c76017c1662fbed9a1cafea5b39e9d6f
diff --git a/src/security/transform/base64-decode.cpp b/src/security/transform/base64-decode.cpp
index 7f3cf54..8b047bc 100644
--- a/src/security/transform/base64-decode.cpp
+++ b/src/security/transform/base64-decode.cpp
@@ -48,7 +48,7 @@
 
   ~Impl()
   {
-    BIO_free_all(m_source);
+    BIO_free_all(m_base64);
   }
 
 public: