Bug Fixes in KDE Base
Fix crash when triggereing the "Compare files" action via D-Bus
If the number of selected items is not two, Dolphin disables this
action. However, it is still possible to trigger it via D-Bus, and this
could cause a crash in DolphinMainWindow::compareFiles() because this
function did not test at all if there are really two items selected.
This patch adds such a check and simplifies the code in that function.