Dolphin doesn't toggle split and close

[chimak111]

In Dolphin (16.04 with kubuntu-backports), if I use "split", the word "split" changes to "close". This doesn't happen in 18.04. One has to click on "split" again to close the active pane.

CAUTION: this is not a full-fledged Kubuntu 18.04 but a minimal Ubuntu iso to which I added plasma-desktop and some other things.

[Snowhog]

It does at here (Kubuntu 18.04; KDE Plasma Version: 5.12.4; KDE Frameworks Version: 5.44.0; Qt Version: 5.9.5; Kernel Version: 4.15.0-17-generic; OS Type: 64-bit; Dolphin Version 17.12.3).