Bug using Roberta models in QA Transformers pipeline.
# 🐛 Bug

Hello, I cant use any roberta model with pipeline('question-answering'), someone can help me in how to fix this issue?

OBS=This error appears just when I use Roberta models.

ERROR:

![image](https://user-images.githubusercontent.com/64150563/82443055-38072700-9a77-11ea-99ac-58316d3e0636.png)


Hi, could you please post a code sample and a textual error, rather than an image? Thanks.<|||||>@LysandreJik yes, its very simple my code I just trying to run a transformers example.

     if __name__ == '__main__':
          import ipywidgets as widgets
          from transformers.pipelines import pipeline
          from transformers.modeling_auto import AutoModelForQuestionAnswering
          from transformers.tokenization_auto import AutoTokenizer

          tokenizer = AutoTokenizer.from_pretrained("deepset/roberta-base-squad2")
          model = AutoModelForQuestionAnswering.from_pretrained("deepset/roberta-base-squad2")
          nlp_qa = pipeline('question-answering', model=model, tokenizer=tokenizer, device = 0)
          X = nlp_qa(context="text document.txt", question='What is this project?')
          print(X)

And runing with this albert or any another albert I got this error:

      File "c:/Users/tioga/Desktop/Tranformers/transformers_test.py", line 44, in <module>
          X = nlp_qa(context=st, question='What is this project?')
      File "C:\Python\lib\site-packages\transformers\pipelines.py", line 1042, in __call__
         for s, e, score in zip(starts, ends, scores)
      File "C:\Python\lib\site-packages\transformers\pipelines.py", line 1042, in <listcomp>
         for s, e, score in zip(starts, ends, scores)
     KeyError: 0
<|||||>I can reproduce this error, but it is working with other models for me. Pinging @tholor who might know what is going on.<|||||>hi guys, anyone managed to understand what the above issue is? I am facing the same issue.
Thanks.<|||||>I believe this was fixed in #4049, which is available in the latest release `v2.10.0`. What are your installed `transformers` versions?<|||||>@LysandreJik I was using 2.7.0, but I still get the same error using 2.10.0<|||||>Using the exact code sample mentioned above? Are you using different code?<|||||>I have the exact issue with one of my Roberta models.. But I tried exact code now
<img width="827" alt="Screen Shot 2020-05-26 at 6 38 24 AM" src="https://user-images.githubusercontent.com/3698879/82908070-50b28980-9f1c-11ea-8a12-ff70f862c46b.png">
<|||||>It's hard for me to test if you give an image. Can you paste the code? If you already have `transformers==2.7.0` installed, your `!pip install transformers==2.10.0` won't work. You need to add the `--upgrade` or `-U` flag.

Can you add

```py
from transformers import __version__
print(__version__)
```

just to make sure?<|||||>@LysandreJik works for me. Thank you.<|||||>Glad I could help!<|||||>This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.
<|||||>Hi,

When I use transformers 2.4.0, it is working without the error, but with 3.0.2  I will get the same error!

So when the context  has the answer in it, everything is fine, when it has not, I get the same error.
Example:

```
from transformers.pipelines import pipeline
name="ktrapeznikov/albert-xlarge-v2-squad-v2"
nlp=pipeline('question-answering',model=name,tokenizer=name,device=-1)
```

This example won't cause any errors and I get the right answer:

```
qa_input =  {'question': 'Is the company listed on any stock exchange?', 'context': 'Roche Corporate Executive Committee on 31 December 2019.  We are dedicated to long-term success. Roche is listed on New York stock exchange.'}
qa_response = nlp(qa_input)
```

This will cause the error:

```
qa_input =  {'question': 'Is the company listed on any stock exchange?', 'context': 'Roche Corporate Executive Committee on 31 December 2019.  We are dedicated to long-term success.'}
qa_response = nlp(qa_input)
```

Can you verify that it is not working with 3.0.2 ?
Do you have any solutions or I should just use older versions for now to work with?

Thanks!
