Fixed a minor codestyle issue.

specreduce/core.py

@@ -181,12 +181,12 @@ def _mask_and_nonfinite_data_handling(
         """
         if mask_treatment not in _ImageParser.implemented_mask_treatment_methods:
             raise ValueError(
-                "`mask_treatment` must be one of "
+                "'mask_treatment' must be one of "
                 f"{_ImageParser.implemented_mask_treatment_methods}"
             )
 
         if mask is not None and (mask.dtype not in (bool, int)):
-            raise ValueError("`mask` must be a boolean or integer array.")
+            raise ValueError("'mask' must be a boolean or integer array.")
 
         match mask_treatment:
             case "apply":
@@ -210,7 +210,7 @@ def _mask_and_nonfinite_data_handling(
             case "apply_nan_only":
                 mask = ~np.isfinite(image)
             case "apply_mask_only":
-                mask = mask if mask is not None else np.zeros(image.shape, dtype=bool)
+                mask = mask.copy() if mask is not None else np.zeros(image.shape, dtype=bool)
 
         if mask.all():
             raise ValueError("Image is fully masked. Check for invalid values.")

specreduce/tests/test_mask_treatment.py

@@ -146,4 +146,4 @@ def test_fully_masked():
     image = mk_image()
     image.mask[:] = 1
     with pytest.raises(ValueError, match="Image is fully masked."):
-        parsed_image = _ImageParser()._parse_image(image, disp_axis=1, mask_treatment="apply")
+        _ImageParser()._parse_image(image, disp_axis=1, mask_treatment="apply")