allow sort input to be missing

Author: twhiteaker

minimal.html

@@ -22,7 +22,6 @@ <h1>Minimal User Interface Example</h1>
       <p>Enter a search term, e.g., groundwater. The user or group with ID <span id="displayId">(not set)</span> will be
          searched.</p>
       <form id="zoteroSearchForm" name="zoteroSearchForm">
-         <input type="hidden" id="sort" name="sort" value="date">
          <input class="search-input" name="q" placeholder="Enter search term" type="text">
          <input type="submit" value="Search">
       </form>

zotero.js

@@ -374,7 +374,10 @@ window.onload = function () {
    document.forms.zoteroSearchForm.q.value = query;
    var itemType = setSelectValue("itemType", itemTypeParam);
    var sort = setSelectValue("visibleSort", sortParam);
-   document.forms.zoteroSearchForm.sort.value = sort;
+   var sortHiddenInput = document.getElementById("sort");
+   if (sortHiddenInput) {
+      document.forms.zoteroSearchForm.sort.value = sort;
+   }
 
    initForm("zoteroSearchForm", expanded);