Fix layout with wrong document type

When navigating from doc1 of type A to doc2 of type B, the following flow is applied:

• load currentDocument
• obsolete layouts of doc type A are updated with currentDocument and potential observers there are called
• new layouts of type B are loaded

If the obsolete layouts have an observer on the current document, there are then executed which can be annoying depending on the executed logic.

Not to mention that it should save some extra template updates.