LDEV-1175 Fixing NullPointerException when referencing adminSync object from Ad…

[cchadwickmc]

This fixes the NullPointerException in Admin.java due to the AdminSync object not being present. We decided to create a new type of AdminSync (AdminSyncNullObject) even though the implementation is identical to AdminSyncNotSupported, just in case there were future plans for AdminSyncNotSupported that would have broken Admin.java when it tried to instantiate one.

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