bugfix for model-mapper & model-router (#3370)

plugins/wasm-go/extensions/model-mapper/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"encoding/json"
 	"errors"
 	"sort"
 	"strings"
@@ -136,11 +137,8 @@ func onHttpRequestHeaders(ctx wrapper.HttpContext, config Config) types.Action {
 			break
 		}
 	}
-	if !matched {
-		return types.ActionContinue
-	}
 
-	if !ctx.HasRequestBody() {
+	if !matched || !ctx.HasRequestBody() {
 		ctx.DontReadRequestBody()
 		return types.ActionContinue
 	}
@@ -158,6 +156,11 @@ func onHttpRequestBody(ctx wrapper.HttpContext, config Config, body []byte) type
 		return types.ActionContinue
 	}
 
+	if !json.Valid(body) {
+		log.Error("invalid json body")
+		return types.ActionContinue
+	}
+
 	oldModel := gjson.GetBytes(body, config.modelKey).String()
 
 	newModel := config.defaultModel