Exception when there is unix_timestamp in CaseWhen

[jackylee-ch]

Describe the bug

java.lang.ClassCastException: org.apache.spark.sql.catalyst.analysis.UnresolvedAttribute cannot be cast to org.apache.spark.sql.catalyst.expressions.AttributeReference
	at com.intel.oap.expression.ConverterUtils$.getResultAttrFromExpr(ConverterUtils.scala:412)
	at com.intel.oap.expression.ConverterUtils$.getResultAttrFromExpr(ConverterUtils.scala:378)
	at com.intel.oap.expression.ColumnarCaseWhen.$anonfun$doColumnarCodeGen$7(ColumnarCaseWhenOperator.scala:73)
	at scala.collection.immutable.List.map(List.scala:297)
	at com.intel.oap.expression.ColumnarCaseWhen.doColumnarCodeGen(ColumnarCaseWhenOperator.scala:73)
	at com.intel.oap.expression.ColumnarAlias.doColumnarCodeGen(ColumnarNamedExpressions.scala:39)
	at com.intel.oap.expression.ColumnarConditionProjector$.$anonfun$init$3(ColumnarConditionProjector.scala:371)

To Reproduce
WSCG is set to true, and the example code is bellow.

select case when a="0" then b else unix_timestamp(a, 'yyyy-MM-dd HH:mm:ss') end time from table limit 10;

Expected behavior
No Exception thrown.

Additional context
None

[PHILO-HE]

Fixed.