UDA fails without input rows

CREATE FUNCTION state_group_and_total(state map<uuid, int>, type uuid)
    RETURNS NULL ON NULL INPUT
    RETURNS map<uuid, int>
    LANGUAGE java AS '
        Integer count = (Integer) state.get(type);

        count = (count == null ? 1 : count + 1);
        state.put(type, count);

        return state;
    ';

CREATE OR REPLACE AGGREGATE group_and_total(uuid)
    SFUNC state_group_and_total
    STYPE map<uuid, int>
    INITCOND {};

SELECT group_and_total("id") FROM mytable;

ERROR [Native-Transport-Requests-1] 2017-04-03 07:25:09,787 Message.java:623 - Unexpected exception during request; channel = [id: 0xd7d9159b, L:/172.19.0.2:9042 - R:/172.19.0.3:43444]
java.lang.AssertionError: null
        at org.apache.cassandra.cql3.functions.UDAggregate$2.compute(UDAggregate.java:189) ~[apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.cql3.selection.AggregateFunctionSelector.getOutput(AggregateFunctionSelector.java:53) ~[apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.cql3.selection.Selection$SelectionWithProcessing$1.getOutputRow(Selection.java:592) ~[apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.cql3.selection.Selection$ResultSetBuilder.getOutputRow(Selection.java:430) ~[apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.cql3.selection.Selection$ResultSetBuilder.build(Selection.java:424) ~[apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.cql3.statements.SelectStatement.process(SelectStatement.java:763) ~[apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.cql3.statements.SelectStatement.processResults(SelectStatement.java:400) ~[apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.cql3.statements.SelectStatement.execute(SelectStatement.java:378) ~[apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.cql3.statements.SelectStatement.execute(SelectStatement.java:251) ~[apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.cql3.statements.SelectStatement.execute(SelectStatement.java:79) ~[apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.cql3.QueryProcessor.processStatement(QueryProcessor.java:217) ~[apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.cql3.QueryProcessor.process(QueryProcessor.java:248) ~[apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.cql3.QueryProcessor.process(QueryProcessor.java:233) ~[apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.transport.messages.QueryMessage.execute(QueryMessage.java:116) ~[apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.transport.Message$Dispatcher.channelRead0(Message.java:517) [apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.transport.Message$Dispatcher.channelRead0(Message.java:410) [apache-cassandra-3.10.jar:3.10]
        at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105) [netty-all-4.0.39.Final.jar:4.0.39.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:366) [netty-all-4.0.39.Final.jar:4.0.39.Final]
        at io.netty.channel.AbstractChannelHandlerContext.access$600(AbstractChannelHandlerContext.java:35) [netty-all-4.0.39.Final.jar:4.0.39.Final]
        at io.netty.channel.AbstractChannelHandlerContext$7.run(AbstractChannelHandlerContext.java:357) [netty-all-4.0.39.Final.jar:4.0.39.Final]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_121]
        at org.apache.cassandra.concurrent.AbstractLocalAwareExecutorService$FutureTask.run(AbstractLocalAwareExecutorService.java:162) [apache-cassandra-3.10.jar:3.10]
        at org.apache.cassandra.concurrent.SEPWorker.run(SEPWorker.java:109) [apache-cassandra-3.10.jar:3.10]
        at java.lang.Thread.run(Thread.java:745) [na:1.8.0_121]