Reverted change introduced in r4910, r4911 didn't fix the problem that was created.

git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@4912 3789f03b-4d11-0410-bbf8-ca57d06f2519
diff --git a/java/com/tigervnc/vncviewer/VncViewer.java b/java/com/tigervnc/vncviewer/VncViewer.java
index bb2cbab..a62d736 100644
--- a/java/com/tigervnc/vncviewer/VncViewer.java
+++ b/java/com/tigervnc/vncviewer/VncViewer.java
@@ -143,8 +143,9 @@
         usage();
       }
 
-      if (vncServerName.getValue() == "")
-        vncServerName.setParam(argv[i]);
+      if (vncServerName.getValue() != null)
+        usage();
+      vncServerName.setParam(argv[i]);
     }
 
   }