Fix SI-7224.

Don't focus positions assigned to the TypeTree of a parent of a Template
when the parent exists in the source. A focused position (instance
of `OffsetPosition`) makes it invisible to the presentation compiler
when it looks for the innermost enclosing tree of a given position
(breaking hyperlinking, for example). See [IDE ticket #1001553](https://scala-ide-portfolio.assembla.com/spaces/scala-ide/tickets/1001553).

(I couldn't find a way to reproduce the pr-ragepos build locally, as I couldn't find the definition of the corresponding Jenkins job)

review by @huitseeker, @hubertp