fix(wechat_qrcode): Init nBytes after the count value is determined (#3480)

fix(wechat_qrcode): Init nBytes after the count value is determined (#3480)

* fix(wechat_qrcode): Initialize nBytes after the count value is determined

* fix(wechat_qrcode): Incorrect count data repair

* chore: format expr

* fix(wechat_qrcode): Avoid null pointer exception

* fix(wechat_qrcode): return when bytes_ is empty

* test(wechat_qrcode): add test case

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Co-authored-by: GZTime <Time.GZ@outlook.com>
Gbp-Pq: Name 0009-fix-wechat_qrcode-Init-nBytes-after-the-count-value-.patch