Fix back button for `document_doctrines#show`

app/views/document/doctrines/show.html.erb

@@ -5,7 +5,11 @@
         <div class="col-lg-12"> 
           <div class="row">
             <div class="col-lg-6">
-              <a href="<%= search_doctrines_path(is_index_table: params[:is_index_table], subject_ids: params[:subject_ids] )%>"> <i class="fas fa-angle-double-left" style="font-size: 20px;color: darkred;" data-bs-toggle="tooltip" data-bs-placement="right" title="Back to index"></i> </a>
+              <% if params[:is_index_table].present? %>
+                <a href="<%= search_doctrines_path(is_index_table: params[:is_index_table], subject_ids: params[:subject_ids] )%>"> <i class="fas fa-angle-double-left" style="font-size: 20px;color: darkred;" data-bs-toggle="tooltip" data-bs-placement="right" title="Back to index"></i> </a>
+              <% else %>
+                <a href="<%= document_path(@document)%>"> <i class="fas fa-angle-double-left" style="font-size: 20px;color: darkred;" data-bs-toggle="tooltip" data-bs-placement="right" title="Back to document"></i> </a>
+              <% end %>
             </div>
             <div class="col-lg-3 text-end"> 
             <b>Date : </b>