fix(application-form): handle no options provided

Users with the right permissions could create a menu with no roles, and
that would cause an error.

Refs: Together-Java#1024

Author: christolis

application/src/main/java/org/togetherjava/tjbot/features/basic/ApplicationCreateCommand.java

@@ -119,7 +119,13 @@ public void onSlashCommand(SlashCommandInteractionEvent event) {
             return;
         }
 
-        long incorrectArgsCount = getIncorrectRoleArgsCount(event.getInteraction().getOptions());
+        final List<OptionMapping> optionMappings = event.getInteraction().getOptions();
+        if (optionMappings.isEmpty()) {
+            event.reply("You have to select at least one role.").setEphemeral(true).queue();
+            return;
+        }
+
+        long incorrectArgsCount = getIncorrectRoleArgsCount(optionMappings);
         if (incorrectArgsCount > 0) {
             event.reply("Missing information for %d roles.".formatted(incorrectArgsCount))
                 .setEphemeral(true)