Replace !goog.isDefAndNotNull() with falsey checks

src/ol/source/imagevectorsource.js

@@ -265,7 +265,7 @@ ol.source.ImageVector.prototype.renderFeature_ =
   } else if (this.styleFunction_) {
     styles = this.styleFunction_(feature, resolution);
   }
-  if (!goog.isDefAndNotNull(styles)) {
+  if (!styles) {
     return false;
   }
   var i, ii, loading = false;

src/ol/source/tileutfgridsource.js

@@ -131,7 +131,7 @@ ol.source.TileUTFGrid.prototype.handleTileJSONResponse = function(tileJSON) {
   this.template_ = tileJSON.template;
 
   var grids = tileJSON.grids;
-  if (!goog.isDefAndNotNull(grids)) {
+  if (!grids) {
     this.setState(ol.source.State.ERROR);
     return;
   }

src/ol/source/vectorsource.js

@@ -705,7 +705,7 @@ ol.source.Vector.prototype.handleFeatureChange_ = function(event) {
   var feature = /** @type {ol.Feature} */ (event.target);
   var featureKey = goog.getUid(feature).toString();
   var geometry = feature.getGeometry();
-  if (!goog.isDefAndNotNull(geometry)) {
+  if (!geometry) {
     if (!(featureKey in this.nullGeometryFeatures_)) {
       if (!goog.isNull(this.featuresRtree_)) {
         this.featuresRtree_.remove(feature);