coverity#1210193 Uninitialized pointer field

Change-Id: I8d9ee48fa7fb08aa7488d891121078024b13bd71

vcl/source/opengl/OpenGLContext.cxx

@@ -21,6 +21,7 @@ using namespace com::sun::star;
 
 OpenGLContext::OpenGLContext():
     mpWindow(NULL),
+    m_pChildWindow(NULL),
     mbInitialized(false)
 {
 }