Using ford with an existing project

I have inherited a very large fortran project and for my own sanity I would like to have some good documentation. I think ford is the right answer.

I am trying to slowly migrate this project over to but I'm to get some advice for how to do this. If I try and run ford on the whole codebase, I get a bunch of parsing errors `'NoneType' object is not subscriptable`.

I also get `Unexpected SUBROUTINE` messages which end up throwing a `NotImplementedError()` which results in

```
File "C:\Users\John.Runburg\AppData\Local\Programs\Python\Python311\Lib\site-packages\ford\fortran_project.py", line 121, in __init__
print(f"Warning: Error parsing {relative_path}.\n\t{e.args[0]}")
~~~~~~^^^
IndexError: tuple index out of range
```
and `Unexpected variable` messages which result in the same as above.

If I throw out only focus on the source files that do not result in these parsing issues, ford makes it to `Correlating information from different parts of your project...` and then throws the error
```
File "C:\Users\John.Runburg\AppData\Local\Programs\Python\Python311\Lib\site-packages\ford\fortran_project.py", line 234, in
module: set(module.deplist)
^^^^^^^^^^^^^^
AttributeError: 'FortranSubmodule' object has no attribute 'deplist'
```

The codebase is written almost entirely in modern fortran. But are there certain features that ford will get hung up on or that commonly cause these kind of problems.

Thanks!