Check that GetData attrref is a cid, not a tid

wb/lib/wb/src/wb_gcg.c

 /* 
- * Proview   $Id: wb_gcg.c,v 1.30 2006-03-31 14:29:39 claes Exp $
+ * Proview   $Id: wb_gcg.c,v 1.31 2006-04-26 07:22:32 claes Exp $
  * Copyright (C) 2005 SSAB Oxelsund AB.
  *
  * This program is free software; you can redistribute it and/or 
@@ -12126,6 +12126,11 @@ vldh_t_node	node;
 	  gcg_error_msg( gcgctx, GSX__REFOBJ, node);  
 	  return GSX__NEXTNODE;
 	}
+	/* Check that this is a class, not a type */
+	if ( !cdh_tidIsCid( class)) {
+	  gcg_error_msg( gcgctx, GSX__REFCLASS, node);  
+	  return GSX__NEXTNODE;
+	}
 
 	/* Insert object in ref list */
 	gcg_aref_insert( gcgctx, refattrref, GCG_PREFIX_REF);