SANS: Removing Cans cause the reduction to fail

[Gesner Passos]

Error reported by the user:

If I do a SANS data reduction with sample & can, but then erase the can run numbers to do just sample alone, will give errors and/or strange results, unless first reload the user file. This has been reported previously.

You can verify this by (tester):
Open SANS->Interface
Set the instrument to LOQ
Add the following files in SingleMode
Load this user file: ​http://trac.mantidproject.org/mantid/attachment/ticket/6070/user_file.txt

set:
sample_sans = 73435
sample_trans = 73390
sample_direct_beam = 73388
can_sans=73434
can_trans=73389
can_direct_beam=73388
(they are inside cycle_12_3)

Execute: Load Data and them 1D Reduce
Remove all the cans values (73434, 73389, 73388)
Execute: 1D Reduce
The reduction will fail with: 'Fatal error found during reduction'.

[Gesner Passos]

There is one bug when executing the reduction with less input files than the previous reduction. The problem, is that the singleton reducer, is not properly cleaned after the reduction and has information about the previous reduction.

SANSRunWindow::handleReduceButtonClick

[Gesner Passos]

Clean the ReductionSingleton for further reductions

Perform a correct cleaning of the ReductionSingleton to not disturb posterior analysis in singlemode. re #6325

Changeset: e88217f1120d2b414018bbeae7aac0655766ce66

[Gesner Passos]

Clean the ReductionSingleton for further reductions

Perform a correct cleaning of the ReductionSingleton to not disturb posterior analysis in singlemode. re #6325

Changeset: 34feb8cd10a8dee73d15ab3f2d27ee67eb732adf

[Nick Draper]

Moved at the code freeze for release 2.4

[Anders Markvardsen]

Followed the easy to follow test and no error was observed

[Stuart Campbell]

This ticket has been transferred to github issue ​7171