ShellPkg/UefiShellLevel2CommansLib: Pointer Resonse should be checked

ShellPkg/UefiShellLevel2CommansLib: Pointer Resonse should be checked

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2049

ShellPkg\Library\UefiShellLevel2CommandsLib\Cp.c line 104 and
ShellPkg\Library\UefiShellLevel2CommandsLib\Mv.c line 640, the
pointer variable Response may be a NULL pointer. So we should
make sure that it isn't NULL before dereference it.

If Response is NULL that indicates a EFI_OUT_OF_RESOURCES
error, directly return SHELL_ABORTED.

Cc: Jaben Carsey <jaben.carsey@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Zhichao Gao <zhichao.gao@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>