Don't Sync() if there is no buffer. This allows derived classes that handle the buffer differently (e.g. reuse the buffer).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@76388 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/stream.cpp

@@ -1488,8 +1488,11 @@ wxFileOffset wxBufferedOutputStream::TellO() const
 
 void wxBufferedOutputStream::Sync()
 {
-    m_o_streambuf->FlushBuffer();
-    m_parent_o_stream->Sync();
+    if (m_o_streambuf)
+    {
+        m_o_streambuf->FlushBuffer();
+        m_parent_o_stream->Sync();
+    }
 }
 
 size_t wxBufferedOutputStream::OnSysWrite(const void *buffer, size_t bufsize)