apps.core.models.node: Fixed issue when saving an existing node in the clean method
apps.core.models.node: Fixed issue when saving an existing node in the clean method

devilry/devilry-django,devilry/devilry-django,vegarang/devilry-django,vegarang/devilry-django,devilry/devilry-django,devilry/devilry-django