(re)introduce hidden checkboxes for undated documents

Author: peterstadler

templates/ajax/correspondence.html

@@ -4,6 +4,7 @@ <h2><a href="#allFilter" class="collapseSingle" aria-expanded="true" data-toggle
         <!-- Facetten Filter-->
         <div class="allFilter panel-collapse collapse show" id="allFilter">
             <div class="input-group facet-group checkbox">
+                <input type="checkbox" name="undated" id="undated" data-template="app:set-facet-checkbox" data-template-key="undated" hidden="hidden"/>
                 <input type="checkbox" name="hideRevealed" id="hideRevealed" data-template="app:set-facet-checkbox" data-template-key="hideRevealed"/>
                 <label for="hideRevealed" data-template="lang:translate">hideRevealedLetters</label>
             </div>

templates/ajax/documents.html

@@ -3,6 +3,7 @@
         <h2><a href="#allFilter" class="collapseSingle" aria-expanded="true" data-toggle="collapse"><span data-template="lang:translate">filter</span></a></h2>
         <!-- Facetten Filter-->
         <div class="allFilter panel-collapse collapse show" id="allFilter">
+            <input type="checkbox" name="undated" id="undated" data-template="app:set-facet-checkbox" data-template-key="undated" hidden="hidden"/>
 
             <h4 data-template="lang:translate">authors</h4>
             <select multiple="multiple" data-template="facets:select" name="authors"/>

templates/ajax/writings.html

@@ -3,6 +3,7 @@
         <h2><a href="#allFilter" class="collapseSingle" aria-expanded="true" data-toggle="collapse"><span data-template="lang:translate">filter</span></a></h2>
         <!-- Facetten Filter-->
         <div class="allFilter panel-collapse collapse show" id="allFilter">
+            <input type="checkbox" name="undated" id="undated" data-template="app:set-facet-checkbox" data-template-key="undated" hidden="hidden"/>
 
             <h4 data-template="lang:translate">authors</h4>
             <select multiple="multiple" data-template="facets:select" name="authors"/>