if (selection === null) {
Seems it will never be true with the filterMouseClicks safeguard. Suggest to address it in another patch as first it's not really related to this patch, and second there is an existing issue with filterMouseClicks (stops the selection start from outside the canvas) probably they can be fixed in the same patch. 

The eventManger has the focus when imageSelector.isSelectorElement(targetNode) is true