Flaky crash in engineering diffraction fitting tab

[warunawickramasingha]

A crash from engineering diffraction GUI's fitting tab was observed during manual testing for mantid v6.12 and it is not a regression issue since the same can be observed in mantid v6.11 as well. Please note that this is flaky to reproduce.

Describe the bug

Delete several workspaces that have been loaded into the fitting tab

1. Load a number of focused files into the Fitting ta with Add to plot ticked.
2. Select a chunk (half or more) workspaces in the ADS and click delete.
3. This error should appear:

Error occurred in handler:
Traceback (most recent call last):
  File "/Applications/MantidWorkbenchNightly.app/Contents/Resources/lib/python3.10/site-packages/mantidqtinterfaces/Engineering/gui/engineering_diffraction/tabs/common/data_handling/data_presenter.py", line 190, in _handle_table_cell_changed
    ws = self.model.get_active_ws(loaded_ws_name)
  File "/Applications/MantidWorkbenchNightly.app/Contents/Resources/lib/python3.10/site-packages/mantidqtinterfaces/Engineering/gui/engineering_diffraction/tabs/common/data_handling/data_model.py", line 90, in get_active_ws
    return self._data_workspaces[loaded_ws_name].get_active_ws()
  File "/Applications/MantidWorkbenchNightly.app/Contents/Resources/lib/python3.10/site-packages/mantidqtinterfaces/Engineering/gui/engineering_diffraction/tabs/common/workspace_record.py", line 46, in __getitem__
    return self.dict[key]
KeyError: 'ENGINX_305794_307521_bank_2_TOF_Fitting'

Expected behavior
No crashes

Screenshots

Platform/Version (please complete the following information):

• OS: [IDAaaS, macOS]
• OS Version:
• Mantid Version [Nightly v6.11.20250117.1720]

Additional context