Left or right key to expand or collapse merges causes view to scroll to the top

[pwalmsley-smtg]

1. Select a merge in the commit view that is already expanded
2. Press the Left key to collapse the merge
3. Press the Right key to expand

EXPECTED: node is expanded and commit stays selected
ACTUAL: node is unchanged and view scrolls to the top

1. Select a merge that is already collapsed
2. Press the Right key to expand
3. Press the Left key to collapse

EXPECTED: node is collapsed and commit stays selected
ACTUAL: node is unchanged and view scrolls to the top.