Hi all,
            Executing,

                        out:format("hello %s", ())

throws Potential bug error. It is clear that 'out:format' function expects an argument of type item(), but this error seems scary :)

Error:
Improper use? Potential bug? Your feedback is welcome:
Contact: basex-talk@mailman.uni-konstanz.de
Version: BaseX 8.1 beta
Java: Oracle Corporation, 1.7.0_75
OS: Linux, amd64
Stack Trace:
java.lang.NullPointerException
    at org.basex.query.func.out.OutFormat.item(OutFormat.java:25)
    at org.basex.query.func.StandardFunc.optimize(StandardFunc.java:80)
    at org.basex.query.func.StandardFunc.compile(StandardFunc.java:74)
    at org.basex.query.MainModule.compile(MainModule.java:73)
    at org.basex.query.QueryCompiler.compile(QueryCompiler.java:113)
    at org.basex.query.QueryCompiler.compile(QueryCompiler.java:104)
    at org.basex.query.QueryContext.analyze(QueryContext.java:323)
    at org.basex.query.QueryContext.compile(QueryContext.java:312)
    at org.basex.query.QueryProcessor.compile(QueryProcessor.java:68)
    at org.basex.core.cmd.AQuery.query(AQuery.java:75)
    at org.basex.core.cmd.XQuery.run(XQuery.java:22)
    at org.basex.core.Command.run(Command.java:379)
    at org.basex.core.Command.execute(Command.java:95)
    at org.basex.gui.GUI.exec(GUI.java:466)
    at org.basex.gui.GUI.access$400(GUI.java:41)
    at org.basex.gui.GUI$7.run(GUI.java:410)
Query:
out:format("hello %s", ())

Best Regards,
Seenivasan