size()==0 -> empty, as recommended by clang-tidy

Core/Computation/ProcessedSample.cpp

Core/Detector/DetectorMask.cpp

Core/Export/OrderedMap.h

Core/Export/SampleToPython.cpp

Core/Export/SimulationToPython.cpp

Core/Fitting/SimDataPair.cpp

Core/HardParticle/FormFactorEllipsoidalCylinder.cpp

Core/HardParticle/FormFactorFullSpheroid.cpp

Core/HardParticle/FormFactorHemiEllipsoid.cpp

Core/Instrument/SimulationResult.h

Core/Intensity/IntensityDataFunctions.cpp

Core/Multilayer/IInterferenceFunctionStrategy.cpp

Core/Parametrization/IParameterized.cpp

Core/Parametrization/ParameterPool.h

Core/Particle/FormFactorWeighted.cpp

Core/Particle/ParticleComposition.cpp

Core/Simulation/DepthProbeSimulation.cpp

Core/Simulation/Simulation.cpp

Fit/Minimizer/MinimizerOptions.cpp

Fit/RootAdapter/MinimizerResultUtils.cpp