Fix the type passed to OpenNSPRFileDesc, no bug

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extra : rebase_source : 68a47b23259d5eaf9171cb9b70adde7720a00727
Bug 784739 - Switch from NULL to nullptr in remaining directories; r=ehsan

--HG--
extra : rebase_source : 1ff19b2c8fd0e77fa8e822f5007a9fa3a6b6d474
Bug 784739 - Switch from NULL to nullptr in js/src/devtools/vprof/ and tools/{jprof,trace-malloc}/; r=ehsan

--HG--
extra : rebase_source : e44e854e1c946c89c38bbef73c53fe8a48510f65