'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)
```

从 page_models.py 第 1356 行附近开始，在二级子页面上复现表单提交，并将其与主页和一级子页面的情况进行比较。跟踪传递给 get_form 的 request 值，并验证表单在每个页面深度都能显示和正常工作，且不会触发报告中的错误。

由索引模型根据 Issue 内容生成。