Index: /trunk/src/VBox/HostServices/SharedOpenGL/crserverlib/server_viewport.c
===================================================================
--- /trunk/src/VBox/HostServices/SharedOpenGL/crserverlib/server_viewport.c	(revision 20027)
+++ /trunk/src/VBox/HostServices/SharedOpenGL/crserverlib/server_viewport.c	(revision 20028)
@@ -279,5 +279,5 @@
 		 crStateViewport( x, y, width, height );
 
-		 mural->viewportValidated = GL_FALSE;
+		 if (mural) mural->viewportValidated = GL_FALSE;
 	}