Is it safe to drive my car without the undertray?

Is it harmful to drive without the undertray? I have a Skoda Yeti and it fell off yesterday. I have a week of work trips before I can get to a garage to replace it.

I'm looking at buying a car with an MoT advisory - should I be worried?

I am thinking of buying a 2014 Hyundai i10. The MoT advisories for 2018/19 say ‘engine covers and undertrays fitted’, otherwise nothing else major. Have they been added by previous owner to conceal something...