Refactoring ineffectual assignments

This patch fixed below 4 types of code line
1. Remove unnecessary variable assignment
2. Use variables declaration instead of explicit initial zero value
3. Change variable name to underbar when variable not used
4. Add erro check and return for ignored error

Signed-off-by: Daehyeok Mun <daehyeok@gmail.com>
Upstream-commit: 6306019d0bad9c4e60ee437e93f2450dfb0b68c0
Component: engine

components/engine/api/types/filters/parse.go

@@ -79,8 +79,8 @@ func ToParamWithVersion(version string, a Args) (string, error) {
 	}
 
 	// for daemons older than v1.10, filter must be of the form map[string][]string
-	buf := []byte{}
-	err := errors.New("")
+	var buf []byte
+	var err error
 	if version != "" && versions.LessThan(version, "1.22") {
 		buf, err = json.Marshal(convertArgsToSlice(a.fields))
 	} else {