a11y: add group role to blocks (#88620)

wcs/blocks.py

@@ -461,7 +461,6 @@ class BlockSubWidget(CompositeWidget):
 class BlockWidget(WidgetList):
     template_name = 'qommon/forms/widgets/block.html'
     always_include_add_button = True
-    a11y_role = 'group'
 
     def __init__(
         self,
@@ -503,6 +502,12 @@ class BlockWidget(WidgetList):
     def a11y_labelledby(self):
         return bool(self.title and self.label_display != 'hidden')
 
+    @property
+    def a11y_role(self):
+        if len([x for x in (self.block.fields or []) if not x.is_no_data_field]) > 1:
+            return 'group'
+        return None
+
     def set_value(self, value):
         from .fields.block import BlockRowValue