Everytime a user switches spatial extent from "Use Active Layer Extent" to something else and back, every layer is added to the combobox, even though they might be already in the list.
So the combobox entries should be cleared before the current layers are added.
Everytime a user switches spatial extent from "Use Active Layer Extent" to something else and back, every layer is added to the combobox, even though they might be already in the list. So the combobox entries should be cleared before the current layers are added.