It's not the amplifier.
The amp probably has a three prong plug.
It will be safe when plugged into a properly wired grounded outlet.

The lamp probably does not have a grounding pin on it's plug. Most don't
My advice is to fix the lamp, or throw it out.
One of it's wires is shorted to the lamp housing.
If that lamp housing is hot, touching it and anything grounded, (guitar amp, sink faucet, radiator, stove, wired telephone, etc.) can kill you!
Sure, you can reverse the lamp plug in it's socket and not get shocked, but it's not worth the risk.

Next time it gets unplugged, re-plugging is a 50 50 risk.

Alive is good!
The E-lectrician
Weezard Reviewed by Weezard on . The Craziest Thing Happened To Me!! So there I was sitting in my dorm room at Montana State University and decided I would get a little light on the subject, so I went to plug my lava lamp in and when I went to do this the plug got pushed back in the wall. So I thought that I would be able to pop it back out without worrying about getting shocked or anything like that, and BOY was I wrong! haha. I took a small screwdriver and very carefully tried to pry the outlet back out of the hole and all of a sudden hit a live wire, and Rating: 5