Fixed uninitialized value problem with setting box vectors. This caused...

Fixed uninitialized value problem with setting box vectors.  This caused sporadic multithreading issues on Linux platforms.

plugins/freeEnergy/platforms/cuda/src/CudaFreeEnergyKernels.cpp

@@ -295,7 +295,7 @@ void CudaFreeEnergyCalcNonbondedSoftcoreForceKernel::initialize(const System& sy
         }
         Vec3 boxVectors[3];
         system.getPeriodicBoxVectors(boxVectors[0], boxVectors[1], boxVectors[2]);
-        //gpuSetPeriodicBoxSize(gpu, static_cast<float>(boxVectors[0][0] ), static_cast<float>(boxVectors[1][1] ), static_cast<float>(boxVectors[2][2] ));
+        gpuSetPeriodicBoxSize(gpu, static_cast<float>(boxVectors[0][0] ), static_cast<float>(boxVectors[1][1] ), static_cast<float>(boxVectors[2][2] ));
         CudaNonbondedMethod method = NO_CUTOFF;
         if (force.getNonbondedMethod() != NonbondedSoftcoreForce::NoCutoff) {
             throw OpenMMException( "NonbondedSoftcoreForce currently only handles NoCutoff option." );