Deal with null images

src/ol/renderer/canvas/canvasimagelayerrenderer.js

@@ -79,8 +79,8 @@ ol.renderer.canvas.ImageLayer.prototype.renderFrame =
   var hints = frameState.viewHints;
 
   if (!hints[ol.ViewHint.ANIMATING] && !hints[ol.ViewHint.PANNING]) {
-    image = imageSource.getImage(
+    image = imageSource.getImage(frameState.extent, viewResolution);
-        frameState.extent, viewResolution);
+    if (!goog.isNull(image)) {
       var imageState = image.getState();
       if (imageState == ol.ImageState.IDLE) {
         goog.events.listenOnce(image, goog.events.EventType.CHANGE,
@@ -90,6 +90,7 @@ ol.renderer.canvas.ImageLayer.prototype.renderFrame =
         this.image_ = image;
       }
     }
+  }
 
   if (!goog.isNull(this.image_)) {
     image = this.image_;

src/ol/renderer/dom/domimagelayerrenderer.js

@@ -68,6 +68,7 @@ ol.renderer.dom.ImageLayer.prototype.renderFrame =
 
   if (!hints[ol.ViewHint.ANIMATING] && !hints[ol.ViewHint.PANNING]) {
     var image_ = imageSource.getImage(frameState.extent, viewResolution);
+    if (!goog.isNull(image_)) {
       var imageState = image_.getState();
       if (imageState == ol.ImageState.IDLE) {
         goog.events.listenOnce(image_, goog.events.EventType.CHANGE,
@@ -77,6 +78,7 @@ ol.renderer.dom.ImageLayer.prototype.renderFrame =
         image = image_;
       }
     }
+  }
 
   if (!goog.isNull(image)) {
     var imageExtent = image.getExtent();

src/ol/renderer/webgl/webglimagelayerrenderer.js

@@ -161,6 +161,7 @@ ol.renderer.webgl.ImageLayer.prototype.renderFrame =
 
   if (!hints[ol.ViewHint.ANIMATING] && !hints[ol.ViewHint.PANNING]) {
     var image_ = imageSource.getImage(frameState.extent, viewResolution);
+    if (!goog.isNull(image_)) {
       var imageState = image_.getState();
       if (imageState == ol.ImageState.IDLE) {
         goog.events.listenOnce(image_, goog.events.EventType.CHANGE,
@@ -179,6 +180,7 @@ ol.renderer.webgl.ImageLayer.prototype.renderFrame =
         }
       }
     }
+  }
 
   if (!goog.isNull(image)) {
     goog.asserts.assert(!goog.isNull(texture));