[BUG] Partial staging (hunks/selected lines) is not working for Amend

[goran-w]

When using the Amend checkbox in Local Changes, the feature of Stage-ing hunks (or selected lines) stops working (or is working oddly).

Unstage-ing hunks (or selected lines) selected lines seem to work, though. Also, Stage/Unstage on whole file seems to work fine - at least until having tried to partially Stage a file.

When trying to Stage a hunk or selected lines, they disappear from the Unstaged diff, but are not added to the Staged diff.