Widget records show sidebar slug instead of label

[Japh]

In Stream 1.4.5, making changes to widgets within a sidebar results in the Context being the sidebar's slug rather than its label.

[Frankie Jarrett]

This is being caused by #514 because connectors are loading on init with a priority of 0, but the widgets_init happens on init with a priority of 1.

I will investigate to ensure we can change this priority without causing regression on #501.