fix(rust/cardano-chain-follower): explicit condition for block roll forward

Author: saibatizoku

rust/cardano-chain-follower/src/follow.rs

@@ -109,9 +109,13 @@ impl ChainFollower {
             }
         }
 
-        if (self.mithril_tip.is_none() || current_mithril_tip > self.mithril_tip)
-            && self.current < self.mithril_tip
-        {
+        let roll_forward_condition = if let Some(mithril_tip) = &self.mithril_tip {
+            current_mithril_tip > *mithril_tip && *mithril_tip > self.current
+        } else {
+            true
+        };
+
+        if roll_forward_condition {
             let snapshot = MithrilSnapshot::new(self.chain);
             if let Some(block) = snapshot.read_block_at(&current_mithril_tip).await {
                 // The Mithril Tip has moved forwards.