[Tree widget] Incorrect category used for element visibility in filtered tree

[saskliutas]

There might be cases where incorrect category is used when determining or changing element visibility in filtered tree. For example ,if we have tree like:

Subject
|- Model
  |- Category A
    |- Element A
      |- Element B (from Category B)

Filter path to Element B will be:
Subject -> Model -> Category A -> Element A -> Element B

At the moment when we try to determine/change visibility of Element B we go up in filter path and look for category. In this particular example we will find Category A and use it. However, Element B is in Category B and it should be used instead in all visibility operations.

Need a way to find real element category instead of the one that is shown in tree as an ancestor.