Fix bug in reflectometry GUI

[raquelalvarezbanos]

Fixes a bug when no transmission runs provided.

To test:

• Open the old reflectometry GUI
• Select INTER and enter run 13460, hit process. The run should be reduced and workspaces 13460_IvsQ, 13460_IvsLam and TOF (this one should be a group with a single entry) should be created in the ADS.
• Reduce a multi-period dataset: select POLREF, enter run 18564 and hit Process, no errors should be shown and the run should be reduced.
• As an extra check, compare results to the new interface.

Fixes #16925.

No need to update release notes, this issue was reported by a developer and picked by squish test.

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[PranavBahuguna]

Code looks fine. I ran the testing instructions - while both 13460 and 18564 could be reduced, I noticed that reducing 18564 would produce the following workspaces:

(Group) 18564
-- 18564_1
-- 18564_2
(Group) 18564_IvsLam
-- 18564_IvsLam_1
-- 18564_IvsLam_2
(Group) 18564_IvsQ
-- 18564_IvsQ_1
-- 18564_IvsQ_2
(Group) 18564_IvsQ_binned
-- 18564_IvsQ_1
-- 18564_IvsQ_2
18564_IvsQ_binned_1
18564_IvsQ_binned_2

The IvsQ and IvsQ_binned groups hold the same IvsQ workspaces and the workspaces that are supposed to be in the IvsQ_binned group are left outside. This appears to happen for any runs processed under POLREF.

[PranavBahuguna]

Actually, the above has nothing to do with your changes.

[raquelalvarezbanos]

Yes, I think it is unrelated to these changes, but given that you found it, I'd like to solve it as part of this PR, so if you could remove the squirrel I'll fix it.

[raquelalvarezbanos]

@PranavBahuguna could you test this again?

[PranavBahuguna]

Alright, workspaces are outputted correctly now.

once checks pass