Refs #5321. Changed return type for generateEmptyMask.

...work/Algorithms/inc/MantidAlgorithms/DetectorDiagnostic.h

Code/Mantid/Framework/Algorithms/src/CreatePSDBleedMask.cpp

Code/Mantid/Framework/Algorithms/src/DetectorDiagnostic.cpp

.../Framework/Algorithms/src/DetectorEfficiencyVariation.cpp

...d/Framework/Algorithms/src/FindDetectorsOutsideLimits.cpp

Code/Mantid/Framework/Algorithms/src/MedianDetectorTest.cpp