Add missing check for return value and be more conservative in constructs to avoid future slips of this kind.
Updated icon!
Fix invalid access when highlighting basename of threads.
Better support for Home and End keys
Improve discoverability of the expand/collapse feature.
It is now accessible via F6 when on tree view (as a bonus, it is
now also reachable via the mouse). The function bar now dynamically
changes to reflect the toggle nature of the tree-view mode (F5)
and the F6 key serves as expand/collapse when on tree mode,
and its previous behavior of bringing up the "Sort By" menu
(which only made sense on non-tree mode). Users wishing to go to
the "Sort By" menu straight from Tree View can still do so with the
"<" and ">" keys (the top-compatible keys for sort selection).