Load failure on loading single spectra with nexus files

[Nick Draper]

From Stephen King

Version: Using Mantid 2.4.0 (1 Feb), but indpendently verified as also present in release of 16 Feb
 
When: Using Load routine to read a single spectrum from a NeXus file
 
Method: Using algorithm from Mantid, or when calling algorithm from Python in Mantid script window
 
Affects: Reading of NeXus files
 
Description: Algorithm works as intended with NeXus files if ONLY READING SPECTRUM 1, or IF READING MORE THAN ONE SPECTRUM. But if you attempt to read only, say, Spectrum 2 the algorithm fails with the following message in the results window:
 
Load started
Error in execution of algorithm LoadISISNexus:
Workspace2D::getSpectrum, histogram number 1 out of range 1
Error in execution of algorithm Load:
Workspace2D::getSpectrum, histogram number 1 out of range 1
 
Reading a single spectrum from a RAW file is unaffected.

[Roman Tolchenov]

Refactored LoadISISNexus slightly

to make it load files with all possible monitor spectra numbers. Re #6595.

Changeset: 4147b5ddf29fb085bb14c9c91689f826d1d17e11

[Roman Tolchenov]

Changed cbegin() to begin(): macs don't like them. Re #6595.

Changeset: f0a95c9b72d9be93c674e4536564c0cab97cb3f3

[Gesner Passos]

Executed LoadISISNexus for LOQ and SANS2D files, asking to load just one spectrum, and it worked, for a range of files/spectrum numbers.

[Stuart Campbell]

This ticket has been transferred to github issue ​7441