NullPointerException with LTRIM, RTRIM and 2-argument SUBSTR() call in GROUP BY clause.

The following query, which fails with a syntax error in 10.1.3 (because functions are not allowed in a GROUP BY expression for 10.1) fails with a NullPointerException in 10.2 and in the codeline (10.3):

create table dt (vc varchar(30));
insert into dt values ('1928-09-21'), ('1903-12-08');
select substr(vc, 3) from dt group by substr(vc, 3);

Result (on trunk) is:

java.lang.NullPointerException
at org.apache.derby.impl.sql.compile.TernaryOperatorNode.isEquivalent(TernaryOperatorNode.java:924)
at org.apache.derby.impl.sql.compile.GroupByList.findGroupingColumn(GroupByList.java:244)
at org.apache.derby.impl.sql.compile.VerifyAggregateExpressionsVisitor.skipChildren(VerifyAggregateExpressionsVisitor.java:146)
at org.apache.derby.impl.sql.compile.TernaryOperatorNode.accept(TernaryOperatorNode.java:497)
at org.apache.derby.impl.sql.compile.ResultColumn.accept(ResultColumn.java:1515)
at org.apache.derby.impl.sql.compile.QueryTreeNodeVector.accept(QueryTreeNodeVector.java:159)
at org.apache.derby.impl.sql.compile.SelectNode.bindExpressions(SelectNode.java:619)
at org.apache.derby.impl.sql.compile.FromSubquery.bindExpressions(FromSubquery.java:262)
at org.apache.derby.impl.sql.compile.FromList.bindExpressions(FromList.java:337)
at org.apache.derby.impl.sql.compile.SelectNode.bindExpressions(SelectNode.java:500)
at org.apache.derby.impl.sql.compile.DMLStatementNode.bindExpressions(DMLStatementNode.java:249)
at org.apache.derby.impl.sql.compile.DMLStatementNode.bind(DMLStatementNode.java:162)
at org.apache.derby.impl.sql.compile.CursorNode.bind(CursorNode.java:253)
at org.apache.derby.impl.sql.GenericStatement.prepMinion(GenericStatement.java:345)
at org.apache.derby.impl.sql.GenericStatement.prepare(GenericStatement.java:119)
at org.apache.derby.impl.sql.conn.GenericLanguageConnectionContext.prepareInternalStatement(GenericLanguageConnectionContext.java:745)
at org.apache.derby.impl.jdbc.EmbedStatement.execute(EmbedStatement.java:568)
at org.apache.derby.impl.jdbc.EmbedStatement.execute(EmbedStatement.java:517)