openAI custom model not work expected

[iptton]

Describe the bug openAI custom model not work as expected

To Reproduce Steps to reproduce the behavior:

1. set custom openai model
2. chat in chat panel
3. reopen setting panel, the openAI model will reset from custom to gpt-3.5-turbo

Expected behavior setting stay "custom"

relate code:

        get() {
            val customModel = AutoDevSettingsState.getInstance().customModel
            if(AutoDevSettingsState.getInstance().openAiModel == SELECT_CUSTOM_MODEL) {
                AutoDevSettingsState.getInstance().openAiModel = customModel
            }
            return  AutoDevSettingsState.getInstance().openAiModel
        }

will reset openAIModel to a unknow value

https://github.com/unit-mesh/auto-dev/commit/e001c12d54ee01b0dcf5ede6b01fa1a4d7891c35