Diff panel is blank when staging only part of a file

How to reproduce:

1. Modify a file by adding two lines (line A, line B)
2. Stage single line only (e.g. line A)
(By now the modified file is still selected in unstaged panel, diff showing remaining changes available to be staged)
3. Select the same file in staged by clicking it
(Diff panel is blank, it should show line A as staged change instead)

When i click the staged file again second time, line A diff now displays correctly.
Then, when i click to select the unstaged file again, the diff view for line B is blank again

This happens to hunks too.