don't throw exceptions if the view is destroyed

`resize()` is a promise, and the `$destroy` event can fire before it finishes, nulling out `scrollView` which subsequently throws an exception because we are trying to call methods on `null`.

Author: ptarjan

js/angular/controller/scrollController.js

@@ -108,43 +108,64 @@ function($scope,
 
   self.scrollTop = function(shouldAnimate) {
     self.resize().then(function() {
+      if (!scrollView) {
+        return;
+      }
       scrollView.scrollTo(0, 0, !!shouldAnimate);
     });
   };
 
   self.scrollBottom = function(shouldAnimate) {
     self.resize().then(function() {
+      if (!scrollView) {
+        return;
+      }
       var max = scrollView.getScrollMax();
       scrollView.scrollTo(max.left, max.top, !!shouldAnimate);
     });
   };
 
   self.scrollTo = function(left, top, shouldAnimate) {
     self.resize().then(function() {
+      if (!scrollView) {
+        return;
+      }
       scrollView.scrollTo(left, top, !!shouldAnimate);
     });
   };
 
   self.zoomTo = function(zoom, shouldAnimate, originLeft, originTop) {
     self.resize().then(function() {
+      if (!scrollView) {
+        return;
+      }
       scrollView.zoomTo(zoom, !!shouldAnimate, originLeft, originTop);
     });
   };
 
   self.zoomBy = function(zoom, shouldAnimate, originLeft, originTop) {
     self.resize().then(function() {
+      if (!scrollView) {
+        return;
+      }
       scrollView.zoomBy(zoom, !!shouldAnimate, originLeft, originTop);
     });
   };
 
   self.scrollBy = function(left, top, shouldAnimate) {
     self.resize().then(function() {
+      if (!scrollView) {
+        return;
+      }
       scrollView.scrollBy(left, top, !!shouldAnimate);
     });
   };
 
   self.anchorScroll = function(shouldAnimate) {
     self.resize().then(function() {
+      if (!scrollView) {
+        return;
+      }
       var hash = $location.hash();
       var elm = hash && $document[0].getElementById(hash);
       if (!(hash && elm)) {