dep: update tm-db to 0.4.0 (#4289)

* dep: update tm-db to 0.4.0

- update 0.4.0 as it is a breaking change and cannot be handled by depndabot

Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>

*  more work towards error handling

* error and emtpy bytes handling

* work on tests

* add changelog entry, change some error handling

* address some pr comments

* panic in a few more places

* move error higher up

* redo some error handling

* fix some bz == nil to len(bz) == 0

* change statebytes

node/node.go

@@ -1158,12 +1158,15 @@ func LoadStateFromDBOrGenesisDocProvider(
 
 // panics if failed to unmarshal bytes
 func loadGenesisDoc(db dbm.DB) (*types.GenesisDoc, error) {
-	b := db.Get(genesisDocKey)
+	b, err := db.Get(genesisDocKey)
+	if err != nil {
+		panic(err)
+	}
 	if len(b) == 0 {
 		return nil, errors.New("genesis doc not found")
 	}
 	var genDoc *types.GenesisDoc
-	err := cdc.UnmarshalJSON(b, &genDoc)
+	err = cdc.UnmarshalJSON(b, &genDoc)
 	if err != nil {
 		panic(fmt.Sprintf("Failed to load genesis doc due to unmarshaling error: %v (bytes: %X)", err, b))
 	}