'str' object has no attribute 'method'

#### Describe the bug
Form input within 2nd level subpages

#### Steps to reproduce

-Home page already has form input
- If a sub page of the site has a form input, nothing happens
- When a second level sub page (root-page/1st-level-subpage/2nd-level-subpage) has form input, error triggers.

#### Expected behavior
The form input should be displayed and works flawlessly, not caring about if it's 1st, 2nd or so on... level of subpages.

#### Additional context

Exception location: _**page_models.py**_ _line_ _**1356**_ _**(if request.method == 'POST':)**_
```
def get_form(self, request, *args, **kwargs):
form_class = self.get_form_class()
form_params = self.get_form_parameters()
form_params.update(kwargs)
if request.method == 'POST':
return form_class(request.POST, request.FILES, *args, **form_params)
return form_class(*args, **form_params)
```

Start with page_models.py around line 1356 and reproduce the form submission on a second-level subpage, comparing it with the home page and first-level subpage cases. Trace the value passed as request to get_form and verify that forms display and work at every page depth without triggering the reported error.

Written by the indexing model from the issue text.