Main/src-client: fix SEGFAULT when returning USB devices and Shared Folders lists.

git-svn-id: http://www.virtualbox.org/svn/vbox/trunk@51765 cfe28804-0f27-0410-a406-dd0f0b0b656f
conflict with branch.

git-svn-id: http://www.virtualbox.org/svn/vbox/trunk@51766 cfe28804-0f27-0410-a406-dd0f0b0b656f
conflict avoidance by more alphabetical sorting.

git-svn-id: http://www.virtualbox.org/svn/vbox/trunk@51767 cfe28804-0f27-0410-a406-dd0f0b0b656f
FE/Qt: Selector UI: Details-pane: Load/Save settings as part of prepare/cleanup logic only.

git-svn-id: http://www.virtualbox.org/svn/vbox/trunk@51768 cfe28804-0f27-0410-a406-dd0f0b0b656f