This simple bash script runs in the background, managing your workspaces and their windows. If you played around with Gnome Shell, you should know what to except - basic rule is to keep the workspaces count to "workspaces occupied by windows + one empty workspace on the end". This way you have never too less or too much spaces.
Technically, if you close all the windows of some middle workspace, then windows from the following spaces will step back by one and the last space will be removed. And if you on the other hand open a new window in the last, empty workspace, a new empty one will appear. Everything is checked with the interval of 1 second.
Requires wmctrl to work.