fix: preserve explicit zero values in native relay requests

relay/channel/perplexity/adaptor.go

@@ -12,6 +12,7 @@ import (
 	relaycommon "github.com/QuantumNous/new-api/relay/common"
 	relayconstant "github.com/QuantumNous/new-api/relay/constant"
 	"github.com/QuantumNous/new-api/types"
+	"github.com/samber/lo"
 
 	"github.com/gin-gonic/gin"
 )
@@ -59,8 +60,8 @@ func (a *Adaptor) ConvertOpenAIRequest(c *gin.Context, info *relaycommon.RelayIn
 	if request == nil {
 		return nil, errors.New("request is nil")
 	}
-	if request.TopP >= 1 {
-		request.TopP = 0.99
+	if lo.FromPtrOr(request.TopP, 0) >= 1 {
+		request.TopP = lo.ToPtr(0.99)
 	}
 	return requestOpenAI2Perplexity(*request), nil
 }