Count in the attachment pane tab is not updated after inplace edition

Reproduction step:

• open a page
• don't switch to the attachments pane
• edit it in place
• upload a new attachment (e.g., upload and insert an image)
• save the page

Expected result:

The attachment pane count is updated.

Actual results:

The attachment pane count is not updated until the user switches to the attachment pane.