fix: 修复事件拉取函数的安全性问题并改进错误处理

修复多个文件中事件拉取函数的安全性问题，添加更健壮的fallback机制
在imageview.lua中改进错误信息显示，确保image变量转换为字符串
在pkg.lua中调整JSON序列化参数以生成更紧凑的输出

data/computercraft/lua/rom/apis/lgui.lua

@@ -592,13 +592,18 @@ end
 
 function GUIManager:handleEvents()
   while self.running do
-    -- Safely get the pullEvent function with fallback to rc.pullEvent
+    -- Safely get the pullEvent function with multiple fallbacks
     local pullEventFunc = os.pullEvent
     if type(pullEventFunc) ~= "function" then
-      -- Try using rc.pullEvent as fallback
-      pullEventFunc = rc and rc.pullEvent
-      if type(pullEventFunc) ~= "function" then
-        error("Neither os.pullEvent nor rc.pullEvent is available")
+      -- Try using rc.pullEvent as fallback if rc is available
+      if rc and type(rc.pullEvent) == "function" then
+        pullEventFunc = rc.pullEvent
+      else
+        -- In CC Tweaked, os.pullEventRaw is always available
+        pullEventFunc = os.pullEventRaw
+        if type(pullEventFunc) ~= "function" then
+          error("No valid event pulling function found. Ensure you're running in a CC Tweaked environment.")
+        end
       end
     end