qedit/nullrenderer: Don't drop csRenderLock in NullRenderer_DoRenderSample().

We don't grab stream_cs to change any variables checked here, except to reset
flush_event, and that cannot result in a deadlock.

The only possible deadlocks here are:

(1) between this function and EndOfStream(), which is correct, as the two
    should presumably be serialized;

(2) between this function and EndFlush(); however, in that case we expect
    BeginFlush() first, which will unblock the streaming thread.

Signed-off-by: Zebediah Figura <z.figura12@gmail.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>

dlls/qedit/nullrenderer.c

@@ -46,9 +46,7 @@ static HRESULT WINAPI NullRenderer_DoRenderSample(struct strmbase_renderer *ifac
         const HANDLE events[2] = {filter->run_event, filter->renderer.flush_event};
 
         SetEvent(filter->renderer.state_event);
-        LeaveCriticalSection(&filter->renderer.csRenderLock);
         WaitForMultipleObjects(2, events, FALSE, INFINITE);
-        EnterCriticalSection(&filter->renderer.csRenderLock);
     }
 
     return S_OK;