Remove goog.isNull in geom classes

src/ol/geom/multilinestring.js

@@ -63,7 +63,7 @@ goog.inherits(ol.geom.MultiLineString, ol.geom.SimpleGeometry);
 ol.geom.MultiLineString.prototype.appendLineString = function(lineString) {
   goog.asserts.assert(lineString.getLayout() == this.layout,
       'layout of lineString should match the layout');
-  if (goog.isNull(this.flatCoordinates)) {
+  if (!this.flatCoordinates) {
     this.flatCoordinates = lineString.getFlatCoordinates().slice();
   } else {
     goog.array.extend(
@@ -270,11 +270,11 @@ ol.geom.MultiLineString.prototype.intersectsExtent = function(extent) {
  */
 ol.geom.MultiLineString.prototype.setCoordinates =
     function(coordinates, opt_layout) {
-  if (goog.isNull(coordinates)) {
+  if (!coordinates) {
     this.setFlatCoordinates(ol.geom.GeometryLayout.XY, null, this.ends_);
   } else {
     this.setLayout(opt_layout, coordinates, 2);
-    if (goog.isNull(this.flatCoordinates)) {
+    if (!this.flatCoordinates) {
       this.flatCoordinates = [];
     }
     var ends = ol.geom.flat.deflate.coordinatess(
@@ -292,9 +292,9 @@ ol.geom.MultiLineString.prototype.setCoordinates =
  */
 ol.geom.MultiLineString.prototype.setFlatCoordinates =
     function(layout, flatCoordinates, ends) {
-  if (goog.isNull(flatCoordinates)) {
-    goog.asserts.assert(!goog.isNull(ends) && ends.length === 0,
-        'ends cannot be null and ends.length should be 0');
+  if (!flatCoordinates) {
+    goog.asserts.assert(ends && ends.length === 0,
+        'ends must be truthy and ends.length should be 0');
   } else if (ends.length === 0) {
     goog.asserts.assert(flatCoordinates.length === 0,
         'flatCoordinates should be an empty array');