Fixes automatic scrolling in multi-column list morphs when the selection is changed.
You can try this out by doing
SoundLibraryTool new openInWorld setExtentFromHalo: 100 asPoint
and using your arrow/Home/End keys to navigate in the sound list.
Reasoning: As per the invariant defined in #setListParameters, listMorphs always includes listMorph. Subsequently, every super send in #selectionIndex: would be without effect because #selectionIndex already has been updated in the child class. Since selection highlighting is also not relevant for multi-column list morphs (this hook is only used by SimpleHierarchicalListMorph), we can refuse this bequest but send #scrollSelectionIntoView manually.
=============== Diff against Morphic-mt.1771 ===============
Item was changed:
----- Method: PluggableMultiColumnListMorph>>selectionIndex: (in category 'selection') -----