Remove goog.isNull in style classes

src/ol/style/atlasmanager.js

@@ -97,13 +97,12 @@ ol.style.AtlasManager.prototype.getInfo = function(id) {
   /** @type {?ol.style.AtlasInfo} */
   var info = this.getInfo_(this.atlases_, id);
 
-  if (goog.isNull(info)) {
+  if (!info) {
     return null;
   }
   /** @type {?ol.style.AtlasInfo} */
   var hitInfo = this.getInfo_(this.hitAtlases_, id);
-  goog.asserts.assert(!goog.isNull(hitInfo),
-      'hitInfo must not be null');
+  goog.asserts.assert(hitInfo, 'hitInfo must not be null');
 
   return this.mergeInfos_(info, hitInfo);
 };
@@ -121,7 +120,7 @@ ol.style.AtlasManager.prototype.getInfo_ = function(atlases, id) {
   for (i = 0, ii = atlases.length; i < ii; ++i) {
     atlas = atlases[i];
     info = atlas.get(id);
-    if (!goog.isNull(info)) {
+    if (info) {
       return info;
     }
   }
@@ -184,7 +183,7 @@ ol.style.AtlasManager.prototype.add =
   /** @type {?ol.style.AtlasInfo} */
   var info = this.add_(false,
       id, width, height, renderCallback, opt_this);
-  if (goog.isNull(info)) {
+  if (!info) {
     return null;
   }
 
@@ -197,8 +196,7 @@ ol.style.AtlasManager.prototype.add =
   /** @type {?ol.style.AtlasInfo} */
   var hitInfo = this.add_(true,
       id, width, height, renderHitCallback, opt_this);
-  goog.asserts.assert(!goog.isNull(hitInfo),
-      'hitInfo must not be null');
+  goog.asserts.assert(hitInfo, 'hitInfo must not be null');
 
   return this.mergeInfos_(info, hitInfo);
 };
@@ -225,9 +223,9 @@ ol.style.AtlasManager.prototype.add_ =
   for (i = 0, ii = atlases.length; i < ii; ++i) {
     atlas = atlases[i];
     info = atlas.add(id, width, height, renderCallback, opt_this);
-    if (!goog.isNull(info)) {
+    if (info) {
       return info;
-    } else if (goog.isNull(info) && i === ii - 1) {
+    } else if (!info && i === ii - 1) {
       // the entry could not be added to one of the existing atlases,
       // create a new atlas that is twice as big and try to add to this one.
       var size;