Colouring item count in groups panel does not work reliably

[AEgit]

JabRef 4.0-dev--snapshot--2017-08-16--maintable-update--69f717336
Windows 10 10.0 amd64
Java 1.8.0_141

When selecting an item in the main table, the associated group (or rather the number giving the number of associated items) should be coloured. This is not the case with newly assigned items. It does appear, however, that this feature is generally buggy - also items that have not been newly assigned to a group are not always coloured in the group panel (sometimes it works, sometimes it does not).
It's difficult for me to replicate this behaviour. As far as I can tell, one way of experiencing reliably this bug is by doing the following.

1. Open a JabRef database
2. Select an item - the associated item count in the groups panel should be coloured (although sometimes it won't)
3. Assign this item to a new group - the item count of the new group will not be coloured

Note, that I've also noticed that colours can "persist" in the main table, although no or only one item is selected. Example:

1. Open a JabRef database
2. Select multiple items which are associated with different groups - the item counts of the different groups should be coloured
3. Now deselect all items and select only one that is associated with a single group - only the item count of that group should be coloured. But actually all item counts of the previously selected items/groups are still coloured.

[lenhard]

@tobiasdiez In order to make addressing this bug a little easier, could you please point me to the code that does the coloring of the group tree? I have a hard time locating it at the moment.

[tobiasdiez]

@lenhard The coloring is determined by pseudo classes that are bound to the anySelectedEntriesMatchedProperty/allSelectedEntriesMatchedProperty of the groups node view model.

[springzfx]

The bug still exists in recent master branch, I fixed this bug in this [commits] (springzfx@a907fb6)

The cause of this bug is that the local variable "pseudoClassState" is garbaged by java gc. There is no reference to this variable except an weak one from "bind" function.