MdeModulePkg: FileExplorerLib: prevent freeing null pointer
MdeModulePkg: FileExplorerLib: prevent freeing null pointer

when there's no volume label 'Info' can be NULL

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael Zimmermann <13027ca0fefa2b406bb0e61c3b36bc21411fbb83@gmail.com>
Reviewed-by: Feng Tian <e66bb7e9f36c82a029035c5885acf75500d07e68@intel.com>

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