"Cannot add sidebar form if sidebar is not visible" error while sidebar is showing

[twschiller]

Describe the bug

• "Cannot add sidebar form if sidebar is not visible" error while sidebar is showing
• The form brick is being shown from a custom trigger

To Reproduce

Steps to reproduce the behavior:

1. Activate the page canvas mod
2. Click on "+ Create"

Actual behavior

An error is show, the form is show, but you can't submit the form

It's happening 100% of the time for @MMirandi? I've been seeing it sporadically

Expected behavior

No error is shown, form is shown and you can submit it

Screenshots/Loom

https://pixiebrix.slack.com/archives/C07DJTPAAHG/p1723830246189949