[chores] Stop JS logic in loci.js if map is not available

This prevents javascript errors if the JS is loaded
on pages where the user doesn't have permission to see the map.

Author: nemesifier

django_loci/static/django-loci/js/loci.js

@@ -570,6 +570,9 @@ django.jQuery(function ($) {
   });
 
   function geometryListeners() {
+    if (!getMap()) {
+      return;
+    }
     var featureGroup = getFeatureGroup(),
       marker = getMarker();
     featureGroup.on("layeradd", function () {