ShellPkg: Initialize the local pointer to avoid potential suspicious dereference.
ShellPkg: Initialize the local pointer to avoid potential suspicious dereference.

1. Initialize the local pointer 'HandleBuffer'.
2. When 'LocateHandleBuffer' return error 'HandleBuffer' is expected unchanged, add code make sure this.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Qiu Shumin <shumin.qiu@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>

git-svn-id: 3158a46dfd52e07d1fda3e32e1ab2e353a00b20f@19229 6f19259b-4bc3-4df7-8a09-765794883524

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