[Fix] PDF initialisation

apps/benchmarks/NonUniformGridCPU/NonUniformGridCPU.cpp

apps/benchmarks/NonUniformGridGPU/NonUniformGridGPU.cpp

apps/benchmarks/UniformGridCPU/UniformGridCPU.py

apps/benchmarks/UniformGridGPU/UniformGridGPU.py

python/lbmpy_walberla/sweep_collection.py

python/lbmpy_walberla/walberla_lbm_package.py

tests/lbm_generated/Example.cpp

tests/lbm_generated/FreeSlipRefinement.cpp

tests/lbm_generated/InterpolationNoSlip.py