Handled SecurityError when accessing iframe in `<GhSiteIframe>`
Handled SecurityError when accessing iframe in `<GhSiteIframe>`

no issue

- when a site has a separate front-end and admin URL the `site` screen could throw errors due to cross-origin access to the iframe content
- detect the error and fall back to a less efficient forced refresh on guid change

TryGhost/Ghost,TryGhost/Ghost,TryGhost/Ghost