Crash when setting long alias for contact

• Briar version: 1.1.6 (4d26628f)
• User feedback: "Renamed user to long username."

Stacktrace:

java.lang.IllegalArgumentException
        at org.briarproject.bramble.contact.ContactManagerImpl.setContactAlias(ContactManagerImpl.java:192)
        at org.briarproject.bramble.contact.ContactManagerImpl.lambda$setContactAlias$4(ContactManagerImpl.java:200)
        at org.briarproject.bramble.contact.-$$Lambda$ContactManagerImpl$EfFGAUvRrCV355yeOOy1D8He3mI.run(lambda)
        at org.briarproject.bramble.db.DatabaseComponentImpl.transaction(DatabaseComponentImpl.java:177)
        at org.briarproject.bramble.contact.ContactManagerImpl.setContactAlias(ContactManagerImpl.java:200)
        at org.briarproject.briar.android.conversation.ConversationViewModel.lambda$setContactAlias$3(ConversationViewModel.java:169)
        at org.briarproject.briar.android.conversation.-$$Lambda$ConversationViewModel$9WfLCS52Gofv6xnFXEVAD-DkifM.run(lambda)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
        at java.lang.Thread.run(Thread.java:761)