Server suggestion setup fails for a message without text

[SquidXTV]

Describe the bug
The bot automatically sets up the up/down votes and a thread to discuss a suggestion.
It fails to do so if someone creates a new post in #server-suggestions without text.
For example: https://discord.com/channels/272761734820003841/480829495486447627/1305554470364643442

Expected behavior
It shouldn't fail, even for posts without text.

To Reproduce

1. Post a new message without text. (only an image for example)
2. See the error

Additional context

One of the EventListeners had an uncaught exception java.lang.IllegalArgumentException: Name may not be empty
  at net.dv8tion.jda.internal.utils.Checks.notEmpty(Checks.java:94)
  at net.dv8tion.jda.internal.entities.channel.mixin.attribute.IThreadContainerMixin.createThreadChannel(IThreadContainerMixin.java:69)
  at net.dv8tion.jda.internal.entities.ReceivedMessage.createThreadChannel(ReceivedMessage.java:946)
  at org.togetherjava.tjbot.features.basic.SuggestionsUpDownVoter.createThread(SuggestionsUpDownVoter.java:70)
  at org.togetherjava.tjbot.features.basic.SuggestionsUpDownVoter.onMessageReceived(SuggestionsUpDownVoter.java:52)
  at org.togetherjava.tjbot.features.system.BotCore.lambda$onMessageReceived$9(BotCore.java:221)
  at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
  at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197)
  at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.jav...

The bot tries to create a new thread and set the title of that thread using the text of the post:

private static void createThread(Message message) {
    String title = message.getContentRaw();

    if (title.length() >= TITLE_MAX_LENGTH) {
        int lastWordEnd = title.lastIndexOf(' ', TITLE_MAX_LENGTH);

        if (lastWordEnd == -1) {
            lastWordEnd = TITLE_MAX_LENGTH;
        }

        title = title.substring(0, lastWordEnd);
    }

    message.createThreadChannel(title).queue();
}

It is missing checks if the text is empty.
What kind of default title would make sense?