Add nil guards to Content_Type and URI

[jdsampayo]

Content-Type

• If the Content-Type header is nil an error is generated trying to extract the first element of the expected Array.
• The preview needs that the Content-Type is at least a blank String otherwise will raise an error: type is required.

URI

• A malformed URI raise an error preventing the preview to render, it is safe to ignore those on the relative URI switcher. example:

<a class="smart-alert" id="smart-link-{{type}}-{{id}}" href="{{action}}">Add Item</a>