Fix "next method" IdeaVim shortcut ]m or [m for PyCharm.

Using a ]m "next method" shortcut always ends with NullPointerException.

This merge request does two things:
1. Fixes of minor deprecation method calling (without editor) `createStructureViewModel` (fixes `AbstracMethodError`
2. Deals with the problem of `navigationOffsets` structure preparation caused by invalid Python PSI Classes hierarchy vs other languages PSI classes hierarchy