fix: handle objects without descriptions in changelog, like detection strategies

Author: elucchesileon

mitreattack/diffStix/changelog_helper.py

@@ -372,15 +372,16 @@ def load_data(self):
 
                         # Description changes
                         #####################
-                        old_lines = old_stix_obj["description"].replace("\n", " ").splitlines()
-                        new_lines = new_stix_obj["description"].replace("\n", " ").splitlines()
-                        old_lines_unique = [line for line in old_lines if line not in new_lines]
-                        new_lines_unique = [line for line in new_lines if line not in old_lines]
-                        if old_lines_unique or new_lines_unique:
-                            html_diff = difflib.HtmlDiff(wrapcolumn=60)
-                            html_diff._legend = ""  # type: ignore[attr-defined]
-                            delta = html_diff.make_table(old_lines, new_lines, "Old Description", "New Description")
-                            new_stix_obj["description_change_table"] = delta
+                        if "description" in old_stix_obj and "description" in new_stix_obj:
+                            old_lines = old_stix_obj["description"].replace("\n", " ").splitlines()
+                            new_lines = new_stix_obj["description"].replace("\n", " ").splitlines()
+                            old_lines_unique = [line for line in old_lines if line not in new_lines]
+                            new_lines_unique = [line for line in new_lines if line not in old_lines]
+                            if old_lines_unique or new_lines_unique:
+                                html_diff = difflib.HtmlDiff(wrapcolumn=60)
+                                html_diff._legend = ""  # type: ignore[attr-defined]
+                                delta = html_diff.make_table(old_lines, new_lines, "Old Description", "New Description")
+                                new_stix_obj["description_change_table"] = delta
 
                         # Relationship changes
                         ######################