#303 Verfication check for empty DBxrefs (ID:0)

[David Osumi-Sutherland]

Can we instigate a check for DBxrefs of the form ID:0. A number of these have slipped though in GO recently.
e.g.- see: https://sourceforge.net/tracker/?func=detail&atid=440764&aid=2799545&group_id=36855
They cause problems for chado loading.

[Nomi Harris]

0 is not the same as null--OE already objects if the ID is literally empty. I have now (2.1-b19) added this test for ID==0. It is done at the same time as the test for ID==null, and both can be turned on/off via the Configure panel for Dbxref Checks in the Verification Manager ("Check for missing ID"). (In other words, the "missing ID" test, which can be turned on or off, now checks for the case where the ID is 0 as well as the check it already did for ID==null; I also added a check for "<new xref>", which previously would be objected to because of the "non-URI" characters < and > but which now is more correctly dinged for being a missing ID.)