NPE when sending private message

Android version: 8.0.0
Phone model: Lenovo K520 (seoul)
Briar version: 1.2.4 (no commit hash, custom package name)

Stacktrace:

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.replace(java.lang.CharSequence, java.lang.CharSequence)' on a null object reference
        at org.briarproject.briar.android.view.TextAttachmentController.onSendEvent(TextAttachmentController.java:107)
        at org.briarproject.briar.android.view.TextSendController.lambda$new$0$TextSendController(TextSendController.java:37)
        at org.briarproject.briar.android.view.-$$Lambda$TextSendController$10Be2Hyuh5TqgqEmcNIq7rn_c-c.onClick(Unknown Source:2)
        at android.view.View.performClick(View.java:6256)
        at android.view.View$PerformClick.run(View.java:24701)
        at android.os.Handler.handleCallback(Handler.java:789)
        at android.os.Handler.dispatchMessage(Handler.java:98)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6653)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:770)

This is a custom build, so the bug may not exist on master.