null out BufferedImage object to make sure it doesn't lead to a memory leak

git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@4795 3789f03b-4d11-0410-bbf8-ca57d06f2519
diff --git a/java/com/tigervnc/rfb/TightDecoder.java b/java/com/tigervnc/rfb/TightDecoder.java
index 38d6362..8c2275f 100644
--- a/java/com/tigervnc/rfb/TightDecoder.java
+++ b/java/com/tigervnc/rfb/TightDecoder.java
@@ -106,6 +106,7 @@
         e.printStackTrace();
       }
       jpeg.getRGB(0, 0, r.width(), r.height(), buf, 0, r.width());
+      jpeg = null;
       handler.imageRect(r, buf);
       return;
     }