fix: Charge locally even if there's an error

relay/channel/gemini/relay-gemini.go

@@ -1355,20 +1355,50 @@ func GeminiChatHandler(c *gin.Context, info *relaycommon.RelayInfo, resp *http.R
 		return nil, types.NewOpenAIError(err, types.ErrorCodeBadResponseBody, http.StatusInternalServerError)
 	}
 	if len(geminiResponse.Candidates) == 0 {
-		// [FIX] Return meaningful error when Candidates is empty
+		usage := dto.Usage{
+			PromptTokens: geminiResponse.UsageMetadata.PromptTokenCount,
+		}
+		usage.CompletionTokenDetails.ReasoningTokens = geminiResponse.UsageMetadata.ThoughtsTokenCount
+		for _, detail := range geminiResponse.UsageMetadata.PromptTokensDetails {
+			if detail.Modality == "AUDIO" {
+				usage.PromptTokensDetails.AudioTokens = detail.TokenCount
+			} else if detail.Modality == "TEXT" {
+				usage.PromptTokensDetails.TextTokens = detail.TokenCount
+			}
+		}
+		if usage.PromptTokens <= 0 {
+			usage.PromptTokens = info.GetEstimatePromptTokens()
+		}
+
+		var newAPIError *types.NewAPIError
 		if geminiResponse.PromptFeedback != nil && geminiResponse.PromptFeedback.BlockReason != nil {
-			return nil, types.NewOpenAIError(
+			newAPIError = types.NewOpenAIError(
 				errors.New("request blocked by Gemini API: "+*geminiResponse.PromptFeedback.BlockReason),
 				types.ErrorCodePromptBlocked,
 				http.StatusBadRequest,
 			)
 		} else {
-			return nil, types.NewOpenAIError(
+			newAPIError = types.NewOpenAIError(
 				errors.New("empty response from Gemini API"),
 				types.ErrorCodeEmptyResponse,
 				http.StatusInternalServerError,
 			)
 		}
+
+		service.ResetStatusCode(newAPIError, c.GetString("status_code_mapping"))
+
+		switch info.RelayFormat {
+		case types.RelayFormatClaude:
+			c.JSON(newAPIError.StatusCode, gin.H{
+				"type":  "error",
+				"error": newAPIError.ToClaudeError(),
+			})
+		default:
+			c.JSON(newAPIError.StatusCode, gin.H{
+				"error": newAPIError.ToOpenAIError(),
+			})
+		}
+		return &usage, nil
 	}
 	fullTextResponse := responseGeminiChat2OpenAI(c, &geminiResponse)
 	fullTextResponse.Model = info.UpstreamModelName
@@ -1643,4 +1673,3 @@ func convertToolChoiceToGeminiConfig(toolChoice any) *dto.ToolConfig {
 	// Unsupported type, return nil
 	return nil
 }
-