don't access Result.error when not error (#4376)

* don't access Result.error when not error

* correct `if` parity

* other error

beacon_chain/validators/validator_duties.nim

@@ -755,10 +755,15 @@ proc proposeBlockMEV(
     # the block failed to validate and integrate into the DAG, which for the
     # purpose of this return value, is equivalent. It's used to drive Beacon
     # REST API output.
+    let errMsg =
+      if unblindedBlockRef.isErr:
+        unblindedBlockRef.error
+      else:
+        "Unblinded block failed either to validate or integrate into validated store: " & unblindedBlockRef.get.error
     warn "proposeBlockMEV: blinded block not successfully unblinded and proposed",
       head = shortLog(head), slot, validator_index,
       validator = shortLog(validator),
-      err = unblindedBlockRef.error, blindedBlck = shortLog(blindedBlock.get)
+      err = errMsg, blindedBlck = shortLog(blindedBlock.get)
     Opt.some head
 
 proc makeBlindedBeaconBlockForHeadAndSlot*(