OrderedDistinct passes join tree row during exec

[max-hoffman]

Re: dolthub/dolt#5700

OrderedDistinct dropped a parent row while executing a join tree, which caused a field index error in the child.

The query below has a slightly different plan, but the OrderedDistinct in the right half of a join tree, with a join SEMI_JOIN(scalarSubq0, scalarSubq1) as a child is the issue.

Project
 ├─ columns: [SUM(xy.x):0!null as SUM(x)]
 └─ GroupBy
     ├─ select: SUM(xy.x:0!null)
     ├─ group: 
     └─ Project
         ├─ columns: [xy.x:0!null, xy.y:1]
         └─ HashJoin
             ├─ Eq
             │   ├─ xy.x:0!null
             │   └─ scalarSubq0.u:2!null
             ├─ Filter
             │   ├─ Eq
             │   │   ├─ xy.x:0!null
             │   │   └─ 2 (tinyint)
             │   └─ Table
             │       ├─ name: xy
             │       └─ columns: [x y]
             └─ HashLookup
                 ├─ source: TUPLE(xy.x:0!null)
                 ├─ target: TUPLE(scalarSubq0.u:0!null)
                 └─ CachedResults
                     └─ OrderedDistinct
                         └─ Project
                             ├─ columns: [scalarSubq0.u:0!null]
                             └─ SemiJoin
                                 ├─ Eq
                                 │   ├─ scalarSubq0.u:2!null
                                 │   └─ scalarSubq1.a:4!null
                                 ├─ TableAlias(scalarSubq0)
                                 │   └─ Table
                                 │       ├─ name: uv
                                 │       └─ columns: [u v]
                                 └─ Filter
                                     ├─ Eq
                                     │   ├─ scalarSubq1.a:0!null
                                     │   └─ 2 (tinyint)
                                     └─ TableAlias(scalarSubq1)
                                         └─ Table
                                             ├─ name: ab
                                             └─ columns: [a]

[zachmu]

LGTM