[Patch] ShellPkg/TftpDynamicCommand: Fix the potentially uninitialized local variable used.

[Jiaxin Wu <Jiaxin.wu@intel.com>]

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1217

Local variable 'Mtftp4Token' might be uninitialized when error happen. This patch is to
resolve the issue.

Cc: Ye Ting <ting.ye@intel.com>
Cc: Fu Siyuan <siyuan.fu@intel.com>
Cc: Carsey Jaben <jaben.carsey@intel.com>
Cc: Zeng Star <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Wu Jiaxin <jiaxin.wu@intel.com>
---
 ShellPkg/DynamicCommand/TftpDynamicCommand/Tftp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/ShellPkg/DynamicCommand/TftpDynamicCommand/Tftp.c b/ShellPkg/DynamicCommand/TftpDynamicCommand/Tftp.c
index c66be6b9d9..d4391b9f33 100644
--- a/ShellPkg/DynamicCommand/TftpDynamicCommand/Tftp.c
+++ b/ShellPkg/DynamicCommand/TftpDynamicCommand/Tftp.c
@@ -934,10 +934,12 @@ DownloadFile (
   DOWNLOAD_CONTEXT      *TftpContext;
   EFI_MTFTP4_TOKEN      Mtftp4Token;
   UINT8                 BlksizeBuf[10];
   UINT8                 WindowsizeBuf[10];
 
+  ZeroMem (&Mtftp4Token, sizeof (EFI_MTFTP4_TOKEN));
+
   // Downloaded file can be large. BS.AllocatePages() is more faster
   // than AllocatePool() and avoid fragmentation.
   // The downloaded file could be an EFI application. Marking the
   // allocated page as EfiBootServicesCode would allow to execute a
   // potential downloaded EFI application.
@@ -959,11 +961,10 @@ DownloadFile (
   }
   TftpContext->FileSize = FileSize;
   TftpContext->DownloadedNbOfBytes   = 0;
   TftpContext->LastReportedNbOfBytes = 0;
 
-  ZeroMem (&Mtftp4Token, sizeof (EFI_MTFTP4_TOKEN));
   Mtftp4Token.Filename    = (UINT8*)AsciiFilePath;
   Mtftp4Token.BufferSize  = FileSize;
   Mtftp4Token.Buffer      = Buffer;
   Mtftp4Token.CheckPacket = CheckPacket;
   Mtftp4Token.Context     = (VOID*)TftpContext;
-- 
2.17.1.windows.2