void vtkOpenGLState::ResetGLClearColorState() { auto& cs = this->Stack.top(); GLfloat fparams[4]; ::glGetFloatv(GL_COLOR_CLEAR_VALUE, fparams); cs.ClearColor[0] = fparams[0]; cs.ClearColor[1] = fparams[1]; cs.ClearColor[2] = fparams[2]; cs.ClearColor[3] = fparams[3]; } it crashed at ::glGetFloatv(GL_COLOR_CLEAR_VALUE, fparams); how can i resolve it?