update changelog PR number and added unit test for Stop() method

changelog.md

@@ -51,7 +51,7 @@
 * [2340](https://github.com/zeta-chain/node/pull/2340) - add ValidateInbound method for cctx orchestrator
 * [2344](https://github.com/zeta-chain/node/pull/2344) - group common data of EVM/Bitcoin signer and observer using base structs
 * [2357](https://github.com/zeta-chain/node/pull/2357) - integrate base Signer structure into EVM/Bitcoin Signer
-* [2359](https://github.com/zeta-chain/node/pull/2357) - integrate base Observer structure into EVM/Bitcoin Observer
+* [2359](https://github.com/zeta-chain/node/pull/2359) - integrate base Observer structure into EVM/Bitcoin Observer
 
 ### Tests
 

zetaclient/chains/base/observer.go

@@ -135,9 +135,11 @@ func (ob *Observer) Stop() {
 	close(ob.stop)
 
 	// close database
-	err := ob.CloseDB()
-	if err != nil {
-		ob.Logger().Chain.Error().Err(err).Msgf("CloseDB failed for chain %d", ob.Chain().ChainId)
+	if ob.db != nil {
+		err := ob.CloseDB()
+		if err != nil {
+			ob.Logger().Chain.Error().Err(err).Msgf("CloseDB failed for chain %d", ob.Chain().ChainId)
+		}
 	}
 	ob.Logger().Chain.Info().Msgf("observer stopped for chain %d", ob.Chain().ChainId)
 }

zetaclient/chains/base/observer_test.go

@@ -132,6 +132,17 @@ func TestNewObserver(t *testing.T) {
 	}
 }
 
+func TestStop(t *testing.T) {
+	t.Run("should be able to stop observer", func(t *testing.T) {
+		// create observer and initialize db
+		ob := createObserver(t)
+		ob.OpenDB(sample.CreateTempDir(t), "")
+
+		// stop observer
+		ob.Stop()
+	})
+}
+
 func TestObserverGetterAndSetter(t *testing.T) {
 	t.Run("should be able to update chain", func(t *testing.T) {
 		ob := createObserver(t)