If the row being removed from the source model isn't shown by KRFPM,
it's correct that we don't need to emit any signals, however we still
need to tell our base class QSFPM so that it updates the mappings
of the visible siblings below that removed row.
Testcase: deleting the Last Search folder in kmail
(full integration test for this testcase will be added to mailcommon).
REVIEW: 128428
BUG: 349789
FIXED-IN: 5.25
0df92439241a76c6a67efa9485bd95c3c25d63a0 by Christian Mollekopf
445453a6ab79a57f5ed2a94ba35afa36fbb8e325 by myself
+ a fix for the runtime warnings with Qt < 5.5, grabbed from Gammaray's copy.
David Faure
Andrey Cygankov
Montel Laurent