dbStruct does not retrieve correctly schema

[nikrou]

On upgrade process, dbStruct registered several changes but don't apply them. The changes are like that :

null in schema blank in database
-2 in schema (-2) in database

I used postgreSQL and don't know if the issue is postgreSQL only or for all databases engine.

dbStruct need to be updated so that upgrade process gives no change if there's any (or if theses changes can not be applied for some reason)

p.s: that ticket is related (for me at least) to ticket:1734