Gitu crashes when a submodule is moved or deleted

After running:

git rm <path/to/submodule>

gitu's main thread panicked with the following information:

thread 'main' panicked at src\git\mod.rs:157:64:
called `Result::unwrap()` on an `Err` value: Expected "<eof>" at byte 318
   note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Similarly, if a repository has a moved submodule, gitu fails to start. The stacktrace is badly formatted with spurious whitespace, so I've omitted it.

> git status
On branch work/modernize
Changes to be committed:
  (use "git restore --staged <file>..." to unstage)
        modified:   .gitmodules
        renamed:    <old/path> -> <new/path>
  [...]

> gitu --print

gitu --print

thread 'main' panicked at src\git\mod.rs:157:64: called `Result::unwrap()` on an `Err` value: Expected "<eof>" at byte 240
                                                                                                                         stack backtrace:
0:     0x7ff70cd966d2 - git_odb_object_data
...

I will try to produce a reproduction repo later when I've got the time.

Start at src/git/mod.rs:157 and reproduce the failure with git rm on a submodule and with a moved submodule. Check that gitu and gitu --print start without panicking and correctly handle the resulting repository state.