[Correctness] test single unique condition (equal) for left anti join using ShuffledHashJoin FAILED

[xumingming]

The following test failed after auron is enabled:

https://github.com/apache/spark/blob/b45f071cd1b653731ae5b1c97c77d1f47560b177/sql/core/src/test/scala/org/apache/spark/sql/execution/joins/ExistenceJoinSuite.scala#L274-L280

stacktrace:

2025-12-31T08:31:30.2143869Z - test single unique condition (equal) for left anti join using ShuffledHashJoin (whole-stage-codegen on) *** FAILED ***
2025-12-31T08:31:30.2144934Z   Results do not match for Spark plan:
2025-12-31T08:31:30.2145515Z    ShuffledHashJoin [a#15], [c#21], LeftAnti, BuildRight
2025-12-31T08:31:30.2146252Z   :- Exchange hashpartitioning(a#15, 1), ENSURE_REQUIREMENTS, [plan_id=3915]
2025-12-31T08:31:30.2146922Z   :  +- Scan ExistingRDD[a#15,b#16]
2025-12-31T08:31:30.2147401Z   +- HashAggregate(keys=[c#21], functions=[], output=[c#21])
2025-12-31T08:31:30.2147841Z      +- Exchange hashpartitioning(c#21, 1), ENSURE_REQUIREMENTS, [plan_id=3911]
2025-12-31T08:31:30.2148295Z         +- HashAggregate(keys=[c#21], functions=[], output=[c#21])
2025-12-31T08:31:30.2148624Z            +- Project [c#21]
2025-12-31T08:31:30.2148867Z               +- Scan ExistingRDD[c#21,d#22]
2025-12-31T08:31:30.2149121Z   
2025-12-31T08:31:30.2149282Z    
2025-12-31T08:31:30.2149445Z    == Results ==
2025-12-31T08:31:30.2149690Z    !== Expected Answer - 4 ==   == Actual Answer - 2 ==
2025-12-31T08:31:30.2150275Z    [1,2.0]                     [1,2.0]
2025-12-31T08:31:30.2150569Z    [1,2.0]                     [1,2.0]
2025-12-31T08:31:30.2150813Z   ![null,5.0]                  
2025-12-31T08:31:30.2151063Z   ![null,null] (SparkPlanTest.scala:95)