Allow user APCs with NULL 'func' (just wake up the thread).

scheduler/synchro.c

@@ -106,7 +106,7 @@ DWORD WINAPI WaitForMultipleObjectsEx( DWORD count, const HANDLE *handles,
         for (i = 0; i < len / sizeof(void*); i += 2)
         {
             PAPCFUNC func = (PAPCFUNC)apc[i];
-            func( (ULONG_PTR)apc[i+1] );
+            if ( func ) func( (ULONG_PTR)apc[i+1] );
         }
     }
     return reply.signaled;

server/thread.c

@@ -482,11 +482,6 @@ void wake_up( struct object *obj, int max )
 int thread_queue_apc( struct thread *thread, void *func, void *param )
 {
     struct thread_apc *apc;
-    if (!func)
-    {
-        SET_ERROR( ERROR_INVALID_PARAMETER );
-        return 0;
-    }
     if (!thread->apc)
     {
         if (!(thread->apc = mem_alloc( MAX_THREAD_APC * sizeof(*apc) )))