fix: test failure (#2874)

core/mapping/unmarshaler.go

@@ -853,10 +853,12 @@ func (u *Unmarshaler) unmarshalWithFullName(m valuerWithParent, v interface{}, f
 
 	numFields := baseType.NumField()
 	for i := 0; i < numFields; i++ {
-		if !baseType.Field(i).IsExported() {
+		field := baseType.Field(i)
+		if !field.IsExported() {
 			continue
 		}
-		if err := u.processField(baseType.Field(i), valElem.Field(i), m, fullName); err != nil {
+
+		if err := u.processField(field, valElem.Field(i), m, fullName); err != nil {
 			return err
 		}
 	}

core/mapping/unmarshaler_test.go

@@ -793,7 +793,9 @@ func TestUnmarshalStringMapFromNotSettableValue(t *testing.T) {
 	}
 
 	ast := assert.New(t)
-	ast.Error(UnmarshalKey(m, &v))
+	ast.NoError(UnmarshalKey(m, &v))
+	assert.Empty(t, v.sort)
+	assert.Nil(t, v.psort)
 }
 
 func TestUnmarshalStringMapFromString(t *testing.T) {