JoinITCase.testInnerJoinOutputWithPk is unstable for POJO type inference

[ERROR] testInnerJoinOutputWithPk(org.apache.flink.table.runtime.stream.table.JoinITCase)  Time elapsed: 0.044 s  <<< ERROR!
org.apache.flink.table.codegen.CodeGenException: Incompatible types of expression and result type. Expression[GeneratedExpression(result$19166,isNull$19167,,GenericType<java.lang.Object>,false)] type is [GenericType<java.lang.Object>], result type is [GenericType<org.apache.flink.table.runtime.utils.CommonTestData.NonPojo>]
	at org.apache.flink.table.codegen.CodeGenerator$$anonfun$generateResultExpression$2.apply(CodeGenerator.scala:379)
	at org.apache.flink.table.codegen.CodeGenerator$$anonfun$generateResultExpression$2.apply(CodeGenerator.scala:377)
	at scala.collection.mutable.ResizableArray$class.foreach(ResizableArray.scala:59)
	at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:48)
	at org.apache.flink.table.codegen.CodeGenerator.generateResultExpression(CodeGenerator.scala:377)
	at org.apache.flink.table.codegen.CodeGenerator.generateConverterResultExpression(CodeGenerator.scala:295)
	at org.apache.flink.table.plan.nodes.datastream.StreamScan$class.generateConversionProcessFunction(StreamScan.scala:115)
	at org.apache.flink.table.plan.nodes.datastream.StreamScan$class.convertToInternalRow(StreamScan.scala:74)
	at org.apache.flink.table.plan.nodes.datastream.DataStreamScan.convertToInternalRow(DataStreamScan.scala:46)