utils/pdf: check radio buttons have kids (#75698)

passerelle/utils/pdf.py

@@ -99,6 +99,7 @@ class Widget:
             self.field_type == pdfrw.PdfName.Btn
             and self.field_flags.is_radio
             and not self.field_flags.is_push_button
+            and self.kids
         ):
             return 'radio'
         elif (
@@ -150,10 +151,14 @@ class Widget:
                 true_values.remove(pdfrw.PdfName.Off)
             return true_values[0]
 
+    @property
+    def kids(self):
+        return self.annotation.Kids or []
+
     @property
     def kids_ordered_by_rect(self):
         assert self.widget_type == 'radio'
-        kids = list(self.annotation.Kids or [])
+        kids = list(self.kids)
 
         def compare(kid1, kid2):
             return rect_compare(Rect.from_pdf_annotation(kid1), Rect.from_pdf_annotation(kid2))