Fix tests

dicebot/src/config.rs

@@ -49,7 +49,7 @@ fn db_path_from_env() -> String {
 }
 
 /// The "bot" section of the config file, for bot settings.
-#[derive(Serialize, Deserialize, Clone, Debug)]
+#[derive(Serialize, Deserialize, Clone, Debug, Default)]
 struct BotConfig {
     /// How far back from current time should we process a message?
     oldest_message_age: Option<u64>,
@@ -189,6 +189,7 @@ mod tests {
             }),
             bot: Some(BotConfig {
                 oldest_message_age: None,
+                ..Default::default()
             }),
         };