refactor: remove redundant locator cleanup in BaseIndex::Init()

Leverage locator.IsNull() to simplify ReadBestBlock() and remove
unnecessary SetNull().

Co-authored-by: furszy <matiasfurszyfer@protonmail.com>
Co-authored-by: l0rinc <pap.lorinc@gmail.com>
Signed-off-by: Hao Xu <hao.xu@linux.dev>

src/index/base.cpp

@@ -59,13 +59,16 @@ BaseIndex::DB::DB(const fs::path& path, size_t n_cache_size, bool f_memory, bool
         .options = [] { DBOptions options; node::ReadDatabaseArgs(gArgs, options); return options; }()}}
 {}
 
-bool BaseIndex::DB::ReadBestBlock(CBlockLocator& locator) const
+CBlockLocator BaseIndex::DB::ReadBestBlock() const
 {
+    CBlockLocator locator;
+
     bool success = Read(DB_BEST_BLOCK, locator);
     if (!success) {
         locator.SetNull();
     }
-    return success;
+
+    return locator;
 }
 
 void BaseIndex::DB::WriteBestBlock(CDBBatch& batch, const CBlockLocator& locator)
@@ -97,10 +100,7 @@ bool BaseIndex::Init()
     // callbacks are not missed once m_synced is true.
     m_chain->context()->validation_signals->RegisterValidationInterface(this);
 
-    CBlockLocator locator;
+    const auto locator{GetDB().ReadBestBlock()};
-    if (!GetDB().ReadBestBlock(locator)) {
-        locator.SetNull();
-    }
 
     LOCK(cs_main);
     CChain& index_chain = m_chainstate->m_chain;

src/index/base.h

@@ -56,7 +56,8 @@ protected:
            bool f_memory = false, bool f_wipe = false, bool f_obfuscate = false);
 
         /// Read block locator of the chain that the index is in sync with.
-        bool ReadBestBlock(CBlockLocator& locator) const;
+        /// Note, the returned locator will be empty if no record exists.
+        CBlockLocator ReadBestBlock() const;
 
         /// Write block locator of the chain that the index is in sync with.
         void WriteBestBlock(CDBBatch& batch, const CBlockLocator& locator);