osg Error osgearth_viewerd fails with "Loaded scene graph does not contain a MapNode

void StateSet::setGlobalDefaults() ShaderPipeline disabled.
void StateSet::setGlobalDefaults() ShaderPipeline disabled.
Error reading file cande.earth: not implemented
osgviewerd: No data loaded

osgearth_viewerd fails with "Loaded scene graph does not contain a MapNode

参考：https://github.com/gwaldron/osgearth/issues/1317