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