If a jury fails to find that a structure entered by defendant was a "building", is that error harmless?

19 Cf. People v. DeSantis (1992) 2 Cal.4th 1198, 1224-1225 and footnote 9, 9 Cal.Rptr.2d 628, 831 P.2d 1210 (no error occurred where burglary instruction failed to require jury to find that the structure entered by defendant was a "building," because only one type of structure -- a house -- was shown by the evidence, and no rational trier of fact could have found that a house was not a building; even if error occurred, it was harmless under Chapman because the defendant admitted that element of the offense).