NPE when multiple values are contained in an IN statement within a CASE statement used in a GROUP BY

An IN statement within a CASE statement within a GROUP BY, that contains more than one element will cause a NPE.

Reproduction Steps:

======== DATA ============

CREATE TABLE Test (
Region VARCHAR(20),
Cost INTEGER
);

INSERT INTO Test VALUES ('Australia', 45);
INSERT INTO Test VALUES ('Asia', 22);
INSERT INTO Test VALUES ('North America', 33);
INSERT INTO Test VALUES ('South America', 55);
INSERT INTO Test VALUES ('Europe', 44);

======= SQL WORKS ===========

SELECT DISTINCT
CASE
WHEN 1 = 0 THEN "REGION"
WHEN "REGION" IN ('Asia') THEN 'A'
ELSE "REGION"
END,
SUM("COST")
FROM TEST
GROUP BY
CASE
WHEN 1 = 0 THEN "REGION"
WHEN "REGION" IN ('Asia') THEN 'A'
ELSE "REGION"
END

============ FAILS ===================

SELECT DISTINCT
CASE
WHEN 1 = 0 THEN "REGION"
WHEN "REGION" IN ('Asia', 'Australia') THEN 'A'
ELSE "REGION"
END,
SUM("COST")
FROM TEST
GROUP BY
CASE
WHEN 1 = 0 THEN "REGION"
WHEN "REGION" IN ('Asia','Australia') THEN 'A'
ELSE "REGION"
END

================== NPE ===================

java.sql.SQLException: Java exception: ': java.lang.NullPointerException'.
at org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.Util.seeNextException(Unknown Source)
at org.apache.derby.impl.jdbc.Util.javaException(Unknown Source)
at org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.TransactionResourceImpl.handleException(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedConnection.handleException(Unknown Source)
at org.apache.derby.impl.jdbc.ConnectionChild.handleException(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedStatement.executeStatement(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedStatement.execute(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedStatement.execute(Unknown Source)
at sun.reflect.GeneratedMethodAccessor47.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:622)
at com.onseven.dbvis.b.B.B.ā(Z:2256)
at com.onseven.dbvis.b.B.F$A.call(Z:2838)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1146)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:701)
Caused by: ERROR XJ001: Java exception: ': java.lang.NullPointerException'.
at org.apache.derby.iapi.error.StandardException.newException(Unknown Source)
at org.apache.derby.impl.jdbc.SQLExceptionFactory.wrapArgsForTransportAcrossDRDA(Unknown Source)
... 22 more
Caused by: java.lang.NullPointerException
at org.apache.derby.exe.acd8cd40bax0152xa074xeeddx0000012ba0d05.e1(Unknown Source)
at org.apache.derby.impl.services.reflect.DirectCall.invoke(Unknown Source)
at org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.doProjection(Unknown Source)
at org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.getNextRowCore(Unknown Source)
at org.apache.derby.impl.sql.execute.SortResultSet.getRowFromResultSet(Unknown Source)
at org.apache.derby.impl.sql.execute.SortResultSet.getNextRowFromRS(Unknown Source)
at org.apache.derby.impl.sql.execute.SortResultSet.loadSorter(Unknown Source)
at org.apache.derby.impl.sql.execute.SortResultSet.openCore(Unknown Source)
at org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl.open(Unknown Source)
at org.apache.derby.impl.sql.GenericPreparedStatement.executeStmt(Unknown Source)
at org.apache.derby.impl.sql.GenericPreparedStatement.execute(Unknown Source)
... 13 more