fix crashing on validation errors

contracts/admin.py

@@ -159,9 +159,14 @@ class ContracteeSignatureRepresentativeInline(
     def get_parent_object_is_editable(self, obj):
         if hasattr(obj, "contract"):
             return obj.contract.is_editable_without_approve_permission
-        else:
+
+        # Crashes if there is invalid input otherwise.
+
+        elif hasattr(obj, "is_editable_without_approve_permission"):
             return obj.is_editable_without_approve_permission
 
+        return False
+
     def get_formset(self, request, obj=None, **kwargs):
         formset = super().get_formset(request, obj, **kwargs)
         formset.request = request
@@ -182,9 +187,14 @@ class SigneeSignatureRepresentativeInline(
     def get_parent_object_is_editable(self, obj):
         if hasattr(obj, "contract"):
             return obj.contract.is_editable_without_approve_permission
-        else:
+
+        # Crashes if there is invalid input otherwise.
+
+        elif hasattr(obj, "is_editable_without_approve_permission"):
             return obj.is_editable_without_approve_permission
 
+        return False
+
     model = SigneeSignatureRepresentative
     extra = 0