mLegacyBootOptionPrivate pointer is initialized in Constructor function
with if condition check, but it's used in Destructor function directly
without any check. Now add the NULL pointer check.
Cc: Eric Dong <eric.dong@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>