is necessary to connect the Mac Mini to a Surge Supressor?

Yes, it's better to be safe than sorry.

I run everything through protected supression and/or UPS 'smoothed' supplies. Mains spikes are rare but they can happen, either due to Transformer failures or local Lightning strikes. I have lost hardware (modems and laptops) that way in the past so now always play it safe.

Go one better ... UPS : Uniterruptible Power Supply.

Many good ones (I have an APC 750 VA model) have a surge-suppressor port for the phoneline to protect your DSL modem and routers.

And UPS gives your unit enough power to run for a few minutes and shut down gracefully rather than "hard", and UPS can keep your modem and router going for a very long time if you take the computer off the UPS.

My informed but still humble opinion.

EDIT: Multiple answers came in while I was typing. My recommendation was the same as them -- a UPS would be better.

A surge protector will protect against surges but not against power interruptions. A momentary power interruption might cause your Mac to shut down or lock up or might mess up a file operation or corrupt memory. A UPS takes over immediately when the house power shuts off and can power your Mac for a few minutes or longer (depending on the size of the UPS). For momentary interruptions it saves you from losing work. For longer interruptions it gives you time to shut everything down properly.

No need to apologize I would think. Repeating a good response only helps the OP.