Fix potential null pointer exception if cursor hotspot isn't available

git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@4886 3789f03b-4d11-0410-bbf8-ca57d06f2519
diff --git a/java/com/tigervnc/vncviewer/DesktopWindow.java b/java/com/tigervnc/vncviewer/DesktopWindow.java
index 362c47a..3aa0dfd 100644
--- a/java/com/tigervnc/vncviewer/DesktopWindow.java
+++ b/java/com/tigervnc/vncviewer/DesktopWindow.java
@@ -128,6 +128,9 @@
 
     hideLocalCursor();
 
+    if (hotspot == null)
+      hotspot = new Point(0, 0);
+
     cursor.hotspot = hotspot;
 
     Dimension bsc = tk.getBestCursorSize(w, h);