Bug 364198

I have created a panel that I use as a dock (looks somewhat similar to the Docky app or the OS X dock). This panel basically have an Application Dashboard widget and Icons-only task manager.
The panel is placed on the bottom edge of the screen and centered, and both minimum and maximum sizes are set. The icons-only task manager item has some launchers pinned. When I open a new app that doesn't have a launcher pinned, and the widgets aren't locked, the last entry in the task manager is missing (it's probably hidden in an invisible row, though I have set the maximum row numbers to 1). When the widgets are locked, all items are present in the task manager, but there is a tiny gap between the last item and the right edge of the panel (tolerable but ugly).

Reproducible: Always

Steps to Reproduce:
1. Create a panel.
2. Put Application Dashboard and Icons-only task manager onto it
3. Set minimum and maximum sizes to the panel
4. Pin some launchers to the task manager (so that their total width is more than the minimum width of the panel)
5. Set maximum number of rows to 1.
6. Open a new app that doesn't have a pinned launcher.
7. If widgets unlocked, the last unpinned entry is missing.

Actual Results:  
The last item in the Icons-only task manager is missing

Expected Results:  
The last item in the Icons-only task manager should be shown

I'm using plasma 5.6 with Kubuntu 16.04 (installed from the backports rep), though the issue was there for the default (older) plasma version as well.