Only check carry over form field if the corresponding preference is turned on

CHANGELOG.rst

@@ -22,6 +22,7 @@ Fixed
 
 * The week overview page was not refreshed when a new week was selected in the dropdown.
 * Make generation of full register printout faster.
+* Updating a lesson documentation caused an error when the preference for carrying over lesson documentations to the whole week was deactivated.
 
 `2.0.1`_ - 2022-02-12
 ---------------------

aleksis/apps/alsijil/forms.py

@@ -58,7 +58,8 @@ class LessonDocumentationForm(forms.ModelForm):
     def save(self, **kwargs):
         lesson_documentation = super(LessonDocumentationForm, self).save(commit=True)
         if (
-            self.cleaned_data["carry_over_week"]
+            get_site_preferences()["alsijil__allow_carry_over_same_week"]
+            and self.cleaned_data["carry_over_week"]
             and (
                 lesson_documentation.topic
                 or lesson_documentation.homework