Is this safe...?

It's going to stress the tank if it's not supported properly. May or may not break, but imagine the mess is it does.

Get a sheet of heavy plywood cut to the size of the tank, and sit that on top of the dresser. Assuming the dresser is strong enough then it should be fine.

It needs to be supported evenly and completely level, or the pressure from the water will eventually cause breaking points. When that happens, you will ruin your floor in addition to killing all your livestock. Get a proper aquarium stand for the size of the tank and do it right.

I agree with whomever told you it's not safe.

You need to have the whole bottom supported, or the glass will eventually crack from being warped by the weight of the water.

put a board under the bottom and on sides off desk because eventually it can break