add PlotlyGeoAssets to window during Plotly.register

for geo AND mapbox base plot modules

... that way we do this only once when geo and mapbox modules
    are registered

Author: etpinard

src/plots/geo/index.js

@@ -37,14 +37,6 @@ function plotGeo(gd) {
     var calcData = gd.calcdata;
     var geoIds = fullLayout._subplots[GEO];
 
-    /**
-     * If 'plotly-geo-assets.js' is not included,
-     * initialize object to keep reference to every loaded topojson
-     */
-    if(window.PlotlyGeoAssets === undefined) {
-        window.PlotlyGeoAssets = {topojson: {}};
-    }
-
     for(var i = 0; i < geoIds.length; i++) {
         var geoId = geoIds[i];
         var geoCalcData = getSubplotCalcData(calcData, GEO, geoId);

src/registry.js

@@ -269,14 +269,25 @@ function registerTraceModule(_module) {
         extendFlat(exports.traceLayoutAttributes, _module.layoutAttributes);
     }
 
-    // add mapbox-gl CSS here to avoid console warning on instantiation
     var basePlotModule = _module.basePlotModule;
-    if(basePlotModule.name === 'mapbox') {
+    var bpmName = basePlotModule.name;
+
+    // add mapbox-gl CSS here to avoid console warning on instantiation
+    if(bpmName === 'mapbox') {
         var styleRules = basePlotModule.constants.styleRules;
         for(var k in styleRules) {
             addStyleRule('.mapboxgl-' + k, styleRules[k]);
         }
     }
+
+    // if `plotly-geo-assets.js` is not included,
+    // add `PlotlyGeoAssets` global to stash references to all fetched
+    // topojson / geojson data
+    if((bpmName === 'geo' || bpmName === 'mapbox') &&
+        (typeof window !== undefined && window.PlotlyGeoAssets === undefined)
+    ) {
+        window.PlotlyGeoAssets = {topojson: {}};
+    }
 }
 
 function registerSubplot(_module) {