TypeError: in_array(): Argument #2 ($haystack) must be of type array, null given in in_array() (line 169 of /var/www/html/web/modules/composer/cas/cas.module)

It looks like FormState's submit handlers should be an array when set, but I think it's possible that they're not set, like if a form doesn't define submit handlers for some reason. Maybe that's the case on your site. That said, I don't think we need the patch written this way. We can just check if getSubmitHandlers is an array first. I'll update that.

bkosborne → changed the visibility of the branch 3.x to hidden.

bkosborne → changed the visibility of the branch 2.x to hidden.

bkosborne → changed the visibility of the branch 3318382-typeerror-inarray-argument to hidden.

accidentally committed to 3.x and reverted it. Created a new branch and committed there instead.

It looks like FormState's submit handlers should be an array when set, but I think it's possible that they're not set, like if a form doesn't define submit handlers for some reason

Looking at FormBuilder, I see a form always initializes the form's submit handlers as array. My guess is that another module alters the form breaks this. The bug is not in CAS module, submit handlers should always come as array. That said, it doesn't hurt if we add this check on CAS code. But, again, I think this has uncovered a bug in other module (or even core) it might be worth investigated.