Add nightmode undefined check for query graphs (#2021)

Affects issues:
- Fixed #2020

Plan/common/src/main/resources/assets/plan/web/js/query.js

@@ -350,7 +350,7 @@ function displayResults(json) {
         order: [[5, "desc"]]
     });
 
-    if (nightmode) {
+    if ('undefined' !== typeof nightmode && nightmode == true) {
         document.querySelector('.table').classList.add('table-dark');
     }
 
@@ -508,4 +508,4 @@ function displayDataResultScreen(resultCount, view) {
                 </div>
             </div>
         </div>`;
-}
+}