string index out of range, then consumes all of my CPU

[ibawt]

java.lang.StringIndexOutOfBoundsException: String index out of range: -17
	at java.lang.String.substring(String.java:1931) ~[?:1.8.0_212]
	at meghanada.server.formatter.SExprOutputFormatter.lambda$autocomplete$3(SExprOutputFormatter.java:178) ~[meghanada-1.2.0.jar:?]
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193) ~[?:1.8.0_212]
	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1382) ~[?:1.8.0_212]
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482) ~[?:1.8.0_212]
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472) ~[?:1.8.0_212]
	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708) ~[?:1.8.0_212]
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[?:1.8.0_212]
	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499) ~[?:1.8.0_212]
	at meghanada.server.formatter.SExprOutputFormatter.autocomplete(SExprOutputFormatter.java:191) ~[meghanada-1.2.0.jar:?]
	at meghanada.server.CommandHandler.autocomplete(CommandHandler.java:189) ~[meghanada-1.2.0.jar:?]
	at meghanada.server.emacs.EmacsServer.lambda$dispatch$2(EmacsServer.java:93) ~[meghanada-1.2.0.jar:?]
	at com.leacox.motif.matching.Matching1.lambda$get$15(Matching1.java:45) ~[meghanada-1.2.0.jar:?]
	at com.leacox.motif.matching.Pattern$1.apply(Pattern.java:40) ~[meghanada-1.2.0.jar:?]
	at com.leacox.motif.matching.FluentMatchingR.getMatch(FluentMatchingR.java:118) ~[meghanada-1.2.0.jar:?]
	at meghanada.server.emacs.EmacsServer.dispatch(EmacsServer.java:350) ~[meghanada-1.2.0.jar:?]
	at meghanada.server.emacs.EmacsServer.lambda$acceptConnection$35(EmacsServer.java:436) ~[meghanada-1.2.0.jar:?]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_212]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_212]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_212]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_212]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_212]