You have a right to work in a safe work environment but that does not necessarily mean that an employer is can be civilly sued for every injury that occurs in the workplace. Most work related injuries are covered by the workers compensation system and preclude civil lawsuits against the employer. That would not prevent you from suing the person who assaulted you.
If there is more to the story than what has been provided, it may be worth it to consult with an employment law attorney regarding workplace safety issues. But based on what you have provided so far, I see no basis for a lawsuit against the employer.
They say you get what you pay for, and this response is free, so take it for what it is worth. This is my opinion based on very limited information. My opinion should not be taken as legal advice. For true advice, we would require a confidential consultation where I would ask you questions and get your complete story. This is a public forum, so remember, nothing here is confidential. Nor am I your attorney. I do not know who you are and you have not hired me to provide any legal service. To do so would require us to meet and sign written retainer agreement. My responses are intended for general information only.
You have the right to a safe work environment but there are a lot of circumstances that will determine whether your employer can be held responsible for the failure to provide it. First, if you were injured, then you would have the right to file a workers compensation claim. You should do that immediately because post termination claims are limited.
Also if you were fired for trying to protect yourself, you may have the right to bring a claim for wrongful termination. However, I would need more facts to establish that. Was this incident forseeable? Did you violate a company policy by tring to restrain fan? You need an lawyer right away.