Don't hide resize handles when expanding selection by holding ctrl and clicking on items

[DamirPorobic]

from: https://phabricator.kde.org/T6321

A final optimization would be to suppress hiding the handles when you are selecting multiple objects, i.e. when Ctrl is pressed.

Let me phrase it differently: When selecting the first item, the current behaviour is fine. When adding a second item to the selection by clicking and keeping Ctrl pressed:

For the second item it should work the same as for the first, i.e. show the handles only after releasing the mouse button. (← That's already the case.)
Always show the handles for the first item, instead of hiding them temporarily when clicking on the second item. (← That would need changing.)

(Basically, I'd imagine it working just like in Inkscape. Perhaps there is also a connection to the previous point, i.e. clicking should only affect the current item in terms of showing the handles.)