422 without scripts in head leads to GET #773
Description
To reproduce
Return a fully rendered 422 from a POST to a form (expected error response) without any scripts in the <head>.
Expected behaviour
Turbo replaces the page body, merges the head and still has scripts available.
Actual behaviour
Turbo decides that the page is ill-formed and makes an unnecessary extra GET request to the same URL.
No warning in the JS console. Nothing in the Rails log.
Config
turbo-rails 2.0.12
rails 7.0.7.2
ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [arm64-darwin21]