Replace goog.isDefAndNotNull() with truthy checks

src/ol/renderer/canvas/canvasvectorlayerrenderer.js

@@ -284,7 +284,7 @@ ol.renderer.canvas.VectorLayer.prototype.prepareFrame =
         styles = styleFunction(feature, resolution);
       }
     }
-    if (goog.isDefAndNotNull(styles)) {
+    if (styles) {
       var dirty = this.renderFeature(
           feature, resolution, pixelRatio, styles, replayGroup);
       this.dirty_ = this.dirty_ || dirty;

src/ol/renderer/dom/domvectorlayerrenderer.js

@@ -292,7 +292,7 @@ ol.renderer.dom.VectorLayer.prototype.prepareFrame =
         styles = styleFunction(feature, resolution);
       }
     }
-    if (goog.isDefAndNotNull(styles)) {
+    if (styles) {
       var dirty = this.renderFeature(
           feature, resolution, pixelRatio, styles, replayGroup);
       this.dirty_ = this.dirty_ || dirty;

src/ol/renderer/layerrenderer.js

@@ -205,7 +205,7 @@ ol.renderer.Layer.prototype.scheduleExpireCache =
  */
 ol.renderer.Layer.prototype.updateAttributions =
     function(attributionsSet, attributions) {
-  if (goog.isDefAndNotNull(attributions)) {
+  if (attributions) {
     var attribution, i, ii;
     for (i = 0, ii = attributions.length; i < ii; ++i) {
       attribution = attributions[i];

src/ol/renderer/webgl/webglvectorlayerrenderer.js

@@ -260,7 +260,7 @@ ol.renderer.webgl.VectorLayer.prototype.prepareFrame =
         styles = styleFunction(feature, resolution);
       }
     }
-    if (goog.isDefAndNotNull(styles)) {
+    if (styles) {
       var dirty = this.renderFeature(
           feature, resolution, pixelRatio, styles, replayGroup);
       this.dirty_ = this.dirty_ || dirty;