This caused problems in the case of find-and-replace:select-all with
multiple editors into the same file.
* a marker is created on the TextBuffer capturing the selection
* DisplayBuffer:create-marker is fired from the first DisplayBuffer.
The marker is turned into a selection which is merged into the current
selection, deleting the marker that was created.
* DisplayBuffer::handleBufferMarkerCreated is called on the second
DisplayBuffer. The marker has been destroyed at this point, so it emits
DisplayBuffer:create-marker with undefined.
* ERROR>
Closes#3364
c3c91ae6c3