Merge branch '32-classes-without-teachers-break-import' into 'master'

Resolve "Classes without teachers break import"

Closes #32

See merge request AlekSIS/official/AlekSIS-App-Untis!97

CHANGELOG.rst

@@ -14,6 +14,11 @@ Changed
 
 * Wrap all imports in complete revisions to make it possible to undo them completely and to track changes correctly.
 
+Fixed
+~~~~~
+
+* Import failed if there were classes without class teachers.
+
 `2.0`_ - 2021-10-30
 -------------------
 

aleksis/apps/untis/util/mysql/importers/common_data.py

@@ -179,7 +179,7 @@ def import_classes(
         # Build values
         short_name = class_.name[:16]
         name = class_.longname if class_.longname else short_name
-        teacher_ids = untis_split_first(class_.teacherids, int)
+        teacher_ids = untis_split_first(class_.teacherids, int) if class_.teacherids else []
         owners = [teachers_ref[t_id] for t_id in teacher_ids]
         import_ref = class_.class_id