Index: /trunk/src/VBox/Main/ConsoleImpl.cpp
===================================================================
--- /trunk/src/VBox/Main/ConsoleImpl.cpp	(revision 24087)
+++ /trunk/src/VBox/Main/ConsoleImpl.cpp	(revision 24088)
@@ -1315,4 +1315,8 @@
     /* mMachine is constant during life time, no need to lock */
     mMachine.queryInterfaceTo(aMachine);
+
+    /* callers expect to get a valid reference, better fail than crash them */
+    if (mMachine.isNull())
+        return E_FAIL;
 
     return S_OK;