fix(claimer): previous too high error

This condition will happen when the checker reads blocks faster than
they are produced, so it shouldn't be considered an error. Instead, the
code just skips the update.

offchain/authority-claimer/src/checker.rs

@@ -67,13 +67,6 @@ pub enum DuplicateCheckerError {
         latest
     ))]
     DepthTooHigh { depth: u64, latest: u64 },
-
-    #[snafu(display(
-        "Previous block `{}` higher than latest block `{}`",
-        previous,
-        latest
-    ))]
-    PreviousTooHigh { previous: u64, latest: u64 },
 }
 
 impl DefaultDuplicateChecker {
@@ -140,13 +133,14 @@ impl DefaultDuplicateChecker {
         ensure!(depth <= latest, DepthTooHighSnafu { depth, latest });
         let latest = latest - depth;
 
-        ensure!(
-            self.next_block_to_read <= latest,
-            PreviousTooHighSnafu {
-                previous: self.next_block_to_read,
+        if latest < self.next_block_to_read {
+            trace!(
+                "nothing to read; next block is {}, but current block is {}",
+                self.next_block_to_read,
                 latest
-            }
-        );
+            );
+            return Ok(());
+        }
 
         let dapp_address = H160(self.dapp_address.inner().to_owned());
         let topic = ValueOrArray::Value(Some(dapp_address.into()));