Index: /trunk/src/VBox/HostServices/SharedOpenGL/render/renderspu.c
===================================================================
--- /trunk/src/VBox/HostServices/SharedOpenGL/render/renderspu.c	(revision 48321)
+++ /trunk/src/VBox/HostServices/SharedOpenGL/render/renderspu.c	(revision 48322)
@@ -1333,5 +1333,6 @@
         renderspuContextRelease(render_spu.defaultSharedContext);
 
-    renderspuContextRetain(pCtx);
+    if (pCtx)
+        renderspuContextRetain(pCtx);
     render_spu.defaultSharedContext = pCtx;
 }