fixed bug where IndexColorModel was reset when switching to 8bpp from another depth

git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@5016 3789f03b-4d11-0410-bbf8-ca57d06f2519
diff --git a/java/com/tigervnc/vncviewer/BIPixelBuffer.java b/java/com/tigervnc/vncviewer/BIPixelBuffer.java
index 6690c79..ae38302 100644
--- a/java/com/tigervnc/vncviewer/BIPixelBuffer.java
+++ b/java/com/tigervnc/vncviewer/BIPixelBuffer.java
@@ -38,7 +38,7 @@
   }
 
   public void updateColourMap() {
-    cm = new IndexColorModel(8, nColours, reds, greens, blues);
+    super.updateColourMap();
     createImage(width_, height_);
   }