virtio-console: fix uninitialized rx virtqueue pointer

[Aphlita]

拉取/合并请求描述：(PR description)

[
本PR用于修复 virtio console 接收路径中可能存在的未初始化指针访问问题。原有代码在使用 rx virtqueue 前未对指针有效性进行显式校验，可能在异常初始化或特殊配置场景下触发静态分析告警甚至运行时风险。本次修改通过在使用前增加空指针检查，确保仅在 rx virtqueue 已正确初始化的情况下继续后续处理，从而提升代码健壮性与可维护性。

为什么提交这份PR (why to submit this PR)

修复 virtio console 接收流程中对 rx virtqueue 的潜在未初始化访问问题，消除静态分析工具报告的 uninitvar 风险，并防止在异常路径下发生空指针解引用。

你的解决方案是什么 (what is your solution)

在访问 rx virtqueue 之前显式检查指针有效性。当 rx virtqueue 为空时直接返回，避免对无效指针及其成员进行访问，其余逻辑保持不变，不影响既有功能行为。

请提供验证的bsp和config (provide the config and bsp)

• BSP:
  bsp/qemu-virt64

• .config:
  CONFIG_RT_USING_VIRTIO=y
  CONFIG_RT_USING_SMP=y

• action:
  https://github.com///actions/workflows/manual_dist.yml
  ]

当前拉取/合并请求的状态 Intent for your PR

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• 本拉取/合并请求是一个草稿版本 This PR is for a code-review and is intended to get feedback
• 本拉取/合并请求是一个成熟版本 This PR is mature, and ready to be integrated into the repo

代码质量 Code Quality：

我在这个拉取/合并请求中已经考虑了 As part of this pull request, I've considered the following:

• 已经仔细查看过代码改动的对比 Already check the difference between PR and old code
• 代码风格正确，包括缩进空格，命名及其他风格 Style guide is adhered to, including spacing, naming and other styles
• 没有垃圾代码，代码尽量精简，不包含#if 0代码，不包含已经被注释了的代码 All redundant code is removed and cleaned up
• 所有变更均有原因及合理的，并且不会影响到其他软件组件代码或BSP All modifications are justified and not affect other components or BSP
• 对难懂代码均提供对应的注释 I've commented appropriately where code is tricky
• 代码是高质量的 Code in this PR is of high quality
• 已经使用formatting 等源码格式化工具确保格式符合RT-Thread代码规范 This PR complies with RT-Thread code specification
• 如果是新增bsp, 已经添加ci检查到.github/ALL_BSP_COMPILE.json 详细请参考链接BSP自查

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[github-actions]

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[github-actions]

📌 Code Review Assignment

🏷️ Tag: components

Reviewers: @Maihuanyi

Changed Files (Click to expand)

• components/drivers/virtio/virtio_console.c

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📊 Current Review Status (Last Updated: 2025-12-14 17:33 CST)

• ⌛ @Maihuanyi Pending Review

---

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[Rbb666]

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