Wouldn't "Yes, there is bread" be correct? Since there is no "gxi" present to refer to a specific "it"?
It can also be non specific. But in this case it is very much specific. The only real logical question would be "Is that bread?" / "Ĉu ĝi estas pano?" to a quick reply of "Yes, it's bread" / "Jes, estas pano".
So the it being indirectly referred to is contextual..
Fair enough, but I still think "Yes, there is bread" would certainly be another acceptable answer.
Cxu estas pano sur la tablo? Jes, estas pano.
Is there bread on the table? Yes, there is bread.