Sets the screenloc property for items in update_icons even if there's no client at the moment (possibly because the player has lost the connection temporarily).
Put the hud_used.hud_shown checks back for hideable inventory slots, preventing the placed items from floating in empty space above the closed inventory.
Added the fix to the back slot, had overlooked it.
Merge pull request #3741 from Rolan7/Issue3643-NoclientIcons

Sets screenloc even if no client