Describe the bug

The workspace dialog appearing on the Elwin interface whenever the Add Workspace is clicked selects workspaces with a valid suffix from the ADS (those with allowed suffix: typically _red and _sqw for Elwin) and displays them on the table.
If from the settings menu of the interface, the option Restrict allowed input files... is unticked, the workspace dialog from the Elwin interface should allow any valid name from the ADS to be added to the elwin interface.

On latest nightly, this option is not working and this seems to be a regression.

To Reproduce

• Add any workspace to the ADS.
• Open Data Processor interface, and on Settings dialog (cog icon) untick the Restrict allowed input files by name checkbox.
• Go to the Elwin tab, click on Add Workspaces, the workspace added to the workspace should be appearing as an entry on the table of this dialog.

Platform/Version (please complete the following information):

• OS: All
• OS Version:
• Mantid Version Nightly

Additional context