P5-1511: Fix for losing image position after navigating back in browser

src/ImageDataHandler.js

@@ -15,11 +15,17 @@ function ImageDataHandler(img) {
 
     this.setCropData = function() {
         var viewportBounds = img.canvas.getViewport().getBounds();
+        if (!viewportBounds) {
+            return;
+        }
+
         var dragAxis = img.canvas.getViewport().getData().axis;
 
         _cropData = {
             x: dragAxis === 'x' ? (viewportBounds.left - img.left) / (img.width * img.scaleX) : 0,
             y: dragAxis === 'y' ? (viewportBounds.top - img.top) / (img.height * img.scaleY) : 0,
+            viewportWidth: viewportBounds.width,
+            viewportHeight: viewportBounds.height,
         };
     };