The order of operations was incorrect.
First the signal that a variable was removed was propagated before the
variable was actually selected.
So e.g. scene item selections would receive the signal that a variable
was deleted but when repopulating the scene item selection the variable
still exists resulting in the list of available entries not to change.
This should make it significantly easier to get an overview of the
variables, which currently exist, modify their settings, or potentially
remove multiple variables.
