ngRepeat: insert end comment only after last element, not after each iterated item

This caused a subtle bug in angular-sortable directive: when moving elements
between lists, previousNode was a comment, which doesn't have the .parentNode
attribute so the $animate.enter function tried to call insertBefore of a null.

Moreover, it looks bad that 'end ngRepeat' comment appears after every iterated
node, it should be just at the end of the repeat block.

Author: Przemek Kaminski

src/ng/directive/ngRepeat.js

@@ -379,7 +379,9 @@ var ngRepeatDirective = ['$parse', '$animate', function($parse, $animate) {
 
             if (!block.startNode) {
               linker(childScope, function(clone) {
-                clone[clone.length++] = document.createComment(' end ngRepeat: ' + expression + ' ');
+                  if(childScope.$last) {
+                    clone[clone.length++] = document.createComment(' end ngRepeat: ' + expression + ' ');
+                  }
                 $animate.enter(clone, null, jqLite(previousNode));
                 previousNode = clone;
                 block.scope = childScope;