continue to catch 404s

modules/renderer/background_source.js

@@ -299,6 +299,11 @@ rendererBackgroundSource.Bing = function(data, dispatch) {
 
 
 rendererBackgroundSource.Esri = function(data) {
+    // in addition to using the tilemap at zoom level 20, overzoom real tiles - #4327 (deprecated technique, but it works)
+    if (data.template.match(/blankTile/) === null) {
+        data.template = data.template + '?blankTile=false';
+    }
+
     var esri = rendererBackgroundSource(data);
     var cache = {};
     var inflight = {};