Merge pull request #1510 from tschaub/bing-providers

Handle case where Bing resource has no imagery providers.

src/ol/source/bingmapssource.js

@@ -115,8 +115,10 @@ ol.source.BingMaps.prototype.handleImageryMetadataResponse =
                     });
               })));
 
+  if (resource.imageryProviders) {
     var transform = ol.proj.getTransformFromProjections(
         ol.proj.get('EPSG:4326'), this.getProjection());
+
     var attributions = goog.array.map(
         resource.imageryProviders,
         function(imageryProvider) {
@@ -146,6 +148,7 @@ ol.source.BingMaps.prototype.handleImageryMetadataResponse =
         });
     attributions.push(ol.source.BingMaps.TOS_ATTRIBUTION);
     this.setAttributions(attributions);
+  }
 
   this.setLogo(brandLogoUri);