ITS#7705,#7800 fix back-mdb pagedResults search

mdb_idscopes was remembering the IDs of every entry it checked;
it should only have been saving the IDs of entries that were
actually in the search scope. The extra entries filled the scopes
array, causing a loop searching for a parent entry that was
never inserted.
ITS#7705,#7800 fix prev commit

Better check for missing IDs