fix: try to fix minimax (close #327)

relay/channel/openai/relay-openai.go

@@ -187,7 +187,7 @@ func OpenaiHandler(c *gin.Context, resp *http.Response, promptTokens int, model
 		return service.OpenAIErrorWrapper(err, "close_response_body_failed", http.StatusInternalServerError), nil
 	}
 
-	if simpleResponse.Usage.TotalTokens == 0 {
+	if simpleResponse.Usage.TotalTokens == 0 || (simpleResponse.Usage.PromptTokens == 0 && simpleResponse.Usage.CompletionTokens == 0) {
 		completionTokens := 0
 		for _, choice := range simpleResponse.Choices {
 			ctkm, _ := service.CountTokenText(string(choice.Message.Content), model)