In the 4.6 beta, and in latest master as of writing this, I'm getting JS errors for notifications.

The notes script that's being loaded is:

http://s1.wp.com/wp-content/mu-plugins/notes/notes-common-v2.js?ver=4.6-beta1-201705

I only notice the JS error when I'm on the Jetpack react pages.

When those pages load, I get this error:

Uncaught TypeError: _.contains is not a function

Then, if I click the notifications button, I get more errors such as:

Uncaught TypeError: this.currentMasterbarActive.addClass is not a function

I'm not sure how to milestone this since all of the milestones were deleted. cc @samhotchkiss cc @dereksmart