Update booting.aspx

Throw the exception immediately if the parameter is not there or empty.

If the parameter is not there it's defaulted to the current url, and this will redirect to itself and create an endless loop here.
Merge pull request #284 from markvantilburg/patch-1

Update booting.aspx
Fix media.save throws an error in Umbraco 7.0.x

See http://issues.umbraco.org/issue/U4-3928 width and Height properties
are assigned on the file media types.  This was because of always
assigning a value to
content.getProperty(uploadFieldConfigNode.WidthFieldAlias).Value

Added an if statement to make sure the media item is an image when
assigning those values.
Merge branch '7.0.2' of https://github.com/rsoeteman/Umbraco-CMS into rsoeteman-7.0.2