Now we delete label 1, given 2 label ids:2,3.
The next call to create a label will do this: it will return the next label id as 2, the size of the array, and thus overwrite the old label 2 with the new label 2. Additionally, since this is a QMap which has a unique key->value, this will prevent any new labels from being added to the area.
Conveniently, this fixes this: