remove default zoomBounds and layerBounds for empty mapmlvectors

Author: yhy0217

src/mapml/layers/FeatureLayer.js

@@ -55,7 +55,9 @@ export var FeatureLayer = L.FeatureGroup.extend({
         this.layerBounds = this.options.layerBounds
           ? this.options.layerBounds
           : null;
-        this.zoomBounds = this.options.zoomBounds;
+        this.zoomBounds = this.options.zoomBounds
+          ? this.options.zoomBounds
+          : null;
       }
     }
   },
@@ -137,9 +139,10 @@ export var FeatureLayer = L.FeatureGroup.extend({
 
   _handleMoveEnd: function () {
     let mapZoom = this._map.getZoom(),
-      withinZoom =
-        mapZoom <= this.zoomBounds.maxZoom &&
-        mapZoom >= this.zoomBounds.minZoom;
+      withinZoom = this.zoomBounds
+        ? mapZoom <= this.zoomBounds.maxZoom &&
+          mapZoom >= this.zoomBounds.minZoom
+        : false;
     this.isVisible =
       withinZoom &&
       this._layers &&
@@ -157,8 +160,8 @@ export var FeatureLayer = L.FeatureGroup.extend({
   _handleZoomEnd: function (e) {
     let mapZoom = this._map.getZoom();
     if (
-      mapZoom > this.zoomBounds.maxZoom ||
-      mapZoom < this.zoomBounds.minZoom
+      this.zoomBounds &&
+      (mapZoom > this.zoomBounds.maxZoom || mapZoom < this.zoomBounds.minZoom)
     ) {
       this.clearLayers();
       return;

src/mapml/layers/MapMLLayer.js

@@ -1515,12 +1515,10 @@ export var MapMLLayer = L.Layer.extend({
           pane: layer._container,
           opacity: layer.options.opacity,
           projection: layer._properties.projection,
-          layerBounds: M.getBounds(layer._content),
           // by NOT passing options.extent, we are asking the FeatureLayer
           // to dynamically update its .layerBounds property as features are
           // added or removed from it
           native: native,
-          zoomBounds: M.getZoomBounds(layer._content, native.zoom),
           // each owned child layer gets a reference to the root layer
           _leafletLayer: layer,
           static: true,