Currently systray popup has a fixed size (can't be resized). If the number of hidden items in systray is greater than 8, all the items over the 8th aren't show in the popup and can't be accessed.

Reproducible: Always

Steps to Reproduce:
1. Open systray config dialog.
2. Set 8 or more plasmoids or apps to "hidden".
3. Open systray popup.

Actual Results:  
All items over the 8th are not visible.

Expected Results:  
Either the popup is resized to show all items or a scroll apperas in the popup.

I've discovered this problem after almost 1 hour trying to make plasma-nm to show on the systray popup. Finally I've realized than the icon always was there but can't be accessed until I remove other items from the popup. So this bug can potentially leave people confused about essential parts of the desktop (networking, bluetooth, removable devices, etc.).