[gui] Incorrect handling of expanding/collapsing tree nodes when a node is selected

[CmP-lt]

When there is a selection in the tree, expanding or collapsing any tree node causes the effect(s) of left click on selected node.

Steps to reproduce

1. Click on any class node in the tree (for the node to become selected and editor tab to be opened).
2. Close opened editor tab.
3. Expand or collapse any node in the tree .

Expected behavior

• Tree node gets expanded/collapsed, state of the editor doesn't get changed.

Observed behavior

• Tree node gets expanded/collapsed, new editor tab for class that is selected in the tree gets opened.

The issue seems to be caused by the change to implementation of getJNodeUnderMouse method in 8271277 (or the fact that here it is called with trySelection parameter being true).

[skylot]

@CmP-lt I commit a fix for this issue, please check 😃

[CmP-lt]

@skylot in latest nightly build expanding/collapsing tree nodes works as expected, thank you.