PaperSignedMapper does not account for lack of signatures in environments where signatures are possible

[jpenilla]

[09:33:03] [CarbonChat Commands Thread #3/ERROR]: [CarbonChat] An unhandled exception was thrown during command execution
java.lang.IllegalStateException: null
	at carbonchat-paper-3.0.0-beta.27.jar/carbonchat.libs.org.incendo.cloud.paper.signed.PaperSignedMapper.apply(PaperSignedMapper.java:99) ~[carbonchat-paper-3.0.0-beta.27.jar:?]
	at carbonchat-paper-3.0.0-beta.27.jar/carbonchat.libs.org.incendo.cloud.paper.signed.PaperSignedMapper.apply(PaperSignedMapper.java:68) ~[carbonchat-paper-3.0.0-beta.27.jar:?]
	at carbonchat-paper-3.0.0-beta.27.jar/carbonchat.libs.org.incendo.cloud.parser.ArgumentParser.lambda$flatMapSuccess$0(ArgumentParser.java:136) ~[carbonchat-paper-3.0.0-beta.27.jar:?]
	at carbonchat-paper-3.0.0-beta.27.jar/carbonchat.libs.org.incendo.cloud.parser.ArgumentParseResult$ParseSuccess.flatMapSuccessFuture(ArgumentParseResult.java:188) ~[carbonchat-paper-3.0.0-beta.27.jar:?]
	at carbonchat-paper-3.0.0-beta.27.jar/carbonchat.libs.org.incendo.cloud.parser.ArgumentParser.lambda$flatMapSuccess$1(ArgumentParser.java:136) ~[carbonchat-paper-3.0.0-beta.27.jar:?]
	at carbonchat-paper-3.0.0-beta.27.jar/carbonchat.libs.org.incendo.cloud.parser.MappedArgumentParserImpl.lambda$parseFuture$0(MappedArgumentParserImpl.java:62) ~[carbonchat-paper-3.0.0-beta.27.jar:?]
	at java.base/java.util.concurrent.CompletableFuture.uniComposeStage(CompletableFuture.java:1187) ~[?:?]
	at java.base/java.util.concurrent.CompletableFuture.thenCompose(CompletableFuture.java:2341) ~[?:?]
	at carbonchat-paper-3.0.0-beta.27.jar/carbonchat.libs.org.incendo.cloud.parser.MappedArgumentParserImpl.parseFuture(MappedArgumentParserImpl.java:62) ~[carbonchat-paper-3.0.0-beta.27.jar:?]
	at carbonchat-paper-3.0.0-beta.27.jar/carbonchat.libs.org.incendo.cloud.minecraft.signed.SignedGreedyStringParser.parseFuture(SignedGreedyStringParser.java:81) ~[carbonchat-paper-3.0.0-beta.27.jar:?]
	at carbonchat-paper-3.0.0-beta.27.jar/carbonchat.libs.org.incendo.cloud.CommandTree.parseArgument(CommandTree.java:593) ~[carbonchat-paper-3.0.0-beta.27.jar:?]
	at carbonchat-paper-3.0.0-beta.27.jar/carbonchat.libs.org.incendo.cloud.CommandTree.attemptParseUnambiguousChild(CommandTree.java:527) ~[carbonchat-paper-3.0.0-beta.27.jar:?]
	at carbonchat-paper-3.0.0-beta.27.jar/carbonchat.libs.org.incendo.cloud.CommandTree.parseCommand(CommandTree.java:256) ~[carbonchat-paper-3.0.0-beta.27.jar:?]
	at carbonchat-paper-3.0.0-beta.27.jar/carbonchat.libs.org.incendo.cloud.CommandTree.lambda$parseCommand$3(CommandTree.java:313) ~[carbonchat-paper-3.0.0-beta.27.jar:?]
	at java.base/java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:1150) ~[?:?]
	at java.base/java.util.concurrent.CompletableFuture$Completion.run(CompletableFuture.java:482) ~[?:?]
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144) ~[?:?]
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642) ~[?:?]
	at java.base/java.lang.Thread.run(Thread.java:1583) ~[?:?]

https://github.com/Incendo/cloud-minecraft/blob/master/cloud-paper-signed-arguments/src/main/java/org/incendo/cloud/paper/signed/PaperSignedMapper.java#L99