Error message finalizing proposal amendments with participatory texts

When finalizing the amendment process of a proposal in a participatory text we received this error (decidim version 0.23.5):

F, [2021-04-28T13:12:10.481323 #10524] FATAL — : [793dca5f-7f9d-4995-89cf-54e2f5883cec] ActionView::Template::Error (undefined method `item' for nil:NilClass):
F, [2021-04-28T13:12:10.481396 #10524] FATAL — : [793dca5f-7f9d-4995-89cf-54e2f5883cec]    54:  <div class="columns mediumlarge-8 large-9">
F, [2021-04-28T13:12:10.481414 #10524] FATAL — : [793dca5f-7f9d-4995-89cf-54e2f5883cec]
F, [2021-04-28T13:12:10.481445 #10524] FATAL — : [793dca5f-7f9d-4995-89cf-54e2f5883cec] decidim-core (0.23.5) app/cells/decidim/diff_cell.rb:38:in `item'

The process finishes correctly but the message displayed to the user : "Completed 500 Internal Server Error". attached extended error message