NPE on "Ctrl-C" from CLI

[shoffmeister]

Upon running kwack for a bit (java -jar ... from local unmodified build), doing some select, some create table as select, I Ctrl+C'ed from kwack, on Linux.

jdbc:duckdb::memory:> 
java.lang.NullPointerException: Cannot read field "conn_ref" because "this.conn" is null
        at org.duckdb.DuckDBPreparedStatement.cancel(DuckDBPreparedStatement.java:350)
        at sqlline.DispatchCallback.forceKillSqlQuery(DispatchCallback.java:83)
        at sqlline.SqlLine.begin(SqlLine.java:616)
        at io.kcache.kwack.KwackEngine.start(KwackEngine.java:263)
        at io.kcache.kwack.KwackEngine.start(KwackEngine.java:255)
        at io.kcache.kwack.KwackMain.call(KwackMain.java:157)
        at io.kcache.kwack.KwackMain.call(KwackMain.java:34)
        at picocli.CommandLine.executeUserObject(CommandLine.java:2045)
        at picocli.CommandLine.access$1500(CommandLine.java:148)
        at picocli.CommandLine$RunLast.executeUserObjectOfLastSubcommandWithSameParent(CommandLine.java:2465)
        at picocli.CommandLine$RunLast.handle(CommandLine.java:2457)
        at picocli.CommandLine$RunLast.handle(CommandLine.java:2419)
        at picocli.CommandLine$AbstractParseResultHandler.execute(CommandLine.java:2277)
        at picocli.CommandLine$RunLast.execute(CommandLine.java:2421)
        at picocli.CommandLine.execute(CommandLine.java:2174)
        at io.kcache.kwack.KwackMain.main(KwackMain.java:297)