Act on copy of this mask array

jdaviz/configs/cubeviz/plugins/spectral_extraction/spectral_extraction.py

@@ -499,7 +499,7 @@ def _extract_from_aperture(self, cube, uncert_cube, mask_cube, aperture,
 
         # Also apply the cube's original mask array
         if mask_cube:
-            mask_from_cube = mask_cube.get_component('flux').data
+            mask_from_cube = mask_cube.get_component('flux').data.copy()
             # Some mask cubes have NaNs where they are not masked instead of 0
             mask_from_cube[np.where(np.isnan(mask_from_cube))] = 0
             mask = np.logical_or(mask, mask_from_cube.astype('bool'))