It's highly illogical to even say "half empty". Through math, we'll work it out with this simple example.
We will say empty is equal to zero, then we'll see full is equal to one. Now, to say half empty, would follow as the proceeding equation, empty divided by 2, which translates to 0/2 when the variables are filled in. The answer to that equation equals zero otherwise known as empty. So by saying half empty means you're saying it's empty.
Now, lets try it with "half full". Obviously our equation for this will be full divided by 2. With variables filled it will be 1/2. Now you're left with one half of full. The way it is meant to be, and should only be.