fix: correct problems with ollama and aider

[yrobla]

It has a pair of problems:

• always need to check that the model contains some value
• only send chunks that contain data, and do not send double newlines as they get considered as a different chunk

Closes: #586

[danbarr]

This resolved the errors I saw with Ollama, however I get pretty unexpected results:

[danbarr]

I think this did something to malicious package detection. Running off this branch, malicious packages aren't being detected at all for me anymore.

[jhrozek]

I think this did something to malicious package detection. Running off this branch, malicious packages aren't being detected at all for me anymore.

Note that if you're running from source, the full malicious database is not available, that's only added when producing the release image. Only packages from https://github.com/stacklok/codegate/blob/main/data/malicious.jsonl and other files in that directory are.

[yrobla]

rebased on top of latest patches, and testing again

please test again, using --model ollama_chat/qwen2.5-coder:7b