ensure we break out if walk back page is 0
ensure we break out if walk back page is 0

this prevents an infinite loop as page was converted to a uint32


Former-commit-id: 0229b0b59846303cad39fc696b2d65a36c544a6d
syscoin/syscoin2,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin