After commit 7781d6ef79, the model of the archive view changed to the
filter model. So we were asking `m_model` to get an index from
`currentIndex`, which instead belongs to `m_filterModel`.
Since the model usage here is pointless (current index = child of the
parent of the current index... why?), just remove the code.
BUG: 379802
FIXED-IN: 17.04.2