Law / Breaking a work contract and preliminary agreement fee in Poland [6]

I have received a job offer from a Polish employer, who claims to have already applied for my work permit.

When I accepted that offer, they made me sign a preliminary agreement stating that if I change my mind, I would have to pay a PLN 10,000 for it. Only after signing it, I realized that there are no penalties assigned to my employer if they change their minds about hiring me. I have read in this forum that my work visa might take too long and my application might get rejected. Moreover, I have no proof that my work permit application has ever been submitted.

My dilemma is, I have been accepted into a master's degree program, and I will soon have to send my decision about it. I am not even sure if I will ever get this visa and this job. Do you guys think that my prospective employer would ever be able to charge me for this preliminary agreement fee if I am a non-European? Are contracts with unilateral fees for breach even legal in Poland?

Thank you for your advice!