fix(workflows): reject malformed step config on remove (#4095)

Assisted-by: GitHub Copilot (model: gpt-5.6-sol, autonomous)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: marcelsafin

src/specify_cli/workflows/catalog.py

@@ -1465,12 +1465,14 @@ def remove_catalog(self, index: int) -> str:
             raise StepValidationError("No step catalog config file found.")
 
         try:
-            data = yaml.safe_load(config_path.read_text(encoding="utf-8")) or {}
+            data = yaml.safe_load(config_path.read_text(encoding="utf-8"))
         except (yaml.YAMLError, OSError, UnicodeDecodeError) as exc:
             raise StepValidationError(
                 f"Catalog config file is unreadable or malformed: {exc}"
             ) from exc
-        if not isinstance(data, dict):
+        if data is None:
+            data = {}
+        elif not isinstance(data, dict):
             raise StepValidationError(
                 "Catalog config file is corrupted (expected a mapping)."
             )

tests/test_workflows.py

@@ -9134,6 +9134,18 @@ def test_remove_catalog_invalid_index(self, project_dir):
         with pytest.raises(StepValidationError, match="out of range"):
             catalog.remove_catalog(5)
 
+    @pytest.mark.parametrize("bad", [[], False, 0, ""])
+    def test_remove_catalog_rejects_falsy_non_mapping_config(
+        self, project_dir, bad
+    ):
+        from specify_cli.workflows.catalog import StepCatalog, StepValidationError
+
+        config_path = project_dir / ".specify" / "step-catalogs.yml"
+        config_path.write_text(yaml.safe_dump(bad), encoding="utf-8")
+
+        with pytest.raises(StepValidationError, match="expected a mapping"):
+            StepCatalog(project_dir).remove_catalog(0)
+
     def test_remove_catalog_no_config(self, project_dir):
         from specify_cli.workflows.catalog import StepCatalog, StepValidationError