1. Change the implementation of function 'LoadVariableFromFile' to return SHELL_STATUS. 2. Add code to check whether the pointer 'FoundVarName' in 'DmpStore.c' is NULL before used.

Signed-off-by: Shumin Qiu <shumin.qiu@intel.com>
Reviewed-by: Ni, Ruiyu <ruiyu.ni@intel.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/ShellPkg@15112 6f19259b-4bc3-4df7-8a09-765794883524