Refs #8587 Fix bad logic causing an exception to be incorrectly thrown

Code/Mantid/Framework/PythonInterface/plugins/algorithms/WorkflowAlgorithms/DensityOfStates.py

@@ -247,7 +247,7 @@ def _read_data_from_file(self, file_name):
 
 			if ( frequencies.size == 0 ):
 				raise ValueError("Failed to load any frequencies from file.")
-			if ( raman_intensities.size == 0 and raman_intensities.size == 0 ):
+			if ( raman_intensities.size == 0 and ir_intensities.size == 0 ):
 				raise ValueError("Failed to load any intensities from file.")
 
 			return frequencies, ir_intensities, raman_intensities, weights