ShellPkg: Do NULL pointer check before the pointer is used.

Do NULL pointer check before the pointer is used to avoid dereferenced.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Qiu Shumin <shumin.qiu@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
diff --git a/ShellPkg/Library/UefiShellLib/UefiShellLib.c b/ShellPkg/Library/UefiShellLib/UefiShellLib.c
index 70852a9..cf89a4a 100644
--- a/ShellPkg/Library/UefiShellLib/UefiShellLib.c
+++ b/ShellPkg/Library/UefiShellLib/UefiShellLib.c
@@ -4071,7 +4071,7 @@
     Status = ShellFileHandleReadLine(Handle, RetVal, &Size, FALSE, Ascii);

 

   }

-  if (Status == EFI_END_OF_FILE && *RetVal != CHAR_NULL) {

+  if (Status == EFI_END_OF_FILE && RetVal != NULL && *RetVal != CHAR_NULL) {

     Status = EFI_SUCCESS;

   }

   if (EFI_ERROR(Status) && (RetVal != NULL)) {