Widget Map override error

[BFoucher]

Description

In my BusinessTemplate I have 3 widget:
widget 1 - (before) - widget 2 - (before) - widget 3
In the BusinessPage children of this BT, I delete the second widget, and after the first.
When I want to create a new widget before the widget 3, the new widget not appears.
If I delete widget 1 and after widget 2, it's work

When i delete the widget2 in first, widgetMap create an override for widget 1 is now before widget 3
When delete the widget 1 this override is not delete and when i create a new widget, this widget_map is this override (before widget 3) but we always have the delete of this override

Related to

Bundle	--	--	--
Analytics		Page
Blog		Query
BusinessEntity		Seo
BusinessPage	✔	Sitemap
Core		Template
Criteria		Twig
Filter		User
Form		ViewReference
I18n		Widget
Media		WidgetMap	✔
UI

[alexislefebvre]

It's related to #982.