Backport: spectrum viewer keyerror no stacks (#2261)

docs/release_notes/2.8.rst

@@ -31,6 +31,7 @@ Fixes
 - #2219: Live viewer: informative error if live directory deleted
 - #2246: Don't duplicate ROI names after stack modification
 - #2250: A bug where a lock object was trying to be pickled has not been fixed, the median filter is now functional.
+- #2242: In the Spectrum Viewer, the Export Tabs now disable when no image stacks are available to prevent a KeyError
 
 Developer Changes
 -----------------
@@ -49,4 +50,4 @@ Developer Changes
 - #2183 : Update CIL to 24.0, numpy 1.23, scipy 1.8
 - #2196 : Cancel in progress test runs when new commit pushed
 - #2213 : unit tests have been added to check that the Time of Flight modes behave correctly when switching between stacks
-- #2250 : Make systems tests stricter to catch operations errors
+- #2250 : Make systems tests stricter to catch operations errors

mantidimaging/gui/windows/spectrum_viewer/presenter.py

@@ -85,6 +85,10 @@ def handle_sample_change(self, uuid: UUID | None) -> None:
         """
         Called when the stack has been changed in the stack selector.
         """
+        if len(self.main_window.presenter.model.datasets) == 0:
+            self.view.exportTabs.setDisabled(True)
+        else:
+            self.view.exportTabs.setDisabled(False)
         if uuid == self.current_stack_uuid:
             return
         else:

mantidimaging/gui/windows/spectrum_viewer/test/presenter_test.py

@@ -7,7 +7,7 @@
 from unittest import mock
 
 import numpy as np
-from PyQt5.QtWidgets import QPushButton, QActionGroup, QGroupBox, QAction, QCheckBox
+from PyQt5.QtWidgets import QPushButton, QActionGroup, QGroupBox, QAction, QCheckBox, QTabWidget
 from parameterized import parameterized
 
 from mantidimaging.core.data.dataset import StrictDataset, MixedDataset
@@ -38,6 +38,7 @@ def setUp(self) -> None:
         self.view.exportButtonRITS = mock.create_autospec(QPushButton)
         self.view.normalise_ShutterCount_CheckBox = mock.create_autospec(QCheckBox)
         self.view.addBtn = mock.create_autospec(QPushButton)
+        self.view.exportTabs = mock.create_autospec(QTabWidget)
         self.view.tof_mode_select_group = mock.create_autospec(QActionGroup)
         self.view.tofPropertiesGroupBox = mock.create_autospec(QGroupBox)
         self.presenter = SpectrumViewerWindowPresenter(self.view, self.main_window)