feat(compiler): gracefully handle empty lists

Author: jbdeboer

lib/compiler.dart

@@ -13,6 +13,8 @@ class Compiler {
   _compileBlock(NodeCursor domCursor, NodeCursor templateCursor,
                List<BlockCache> blockCaches,
                List<DirectiveRef> useExistingDirectiveRefs) {
+    if (domCursor.nodeList().length == 0) return null;
+
     var directivePositions = null; // don't pre-create to create spars tree and prevent GC pressure.
     var cursorAlreadyAdvanced;
 

lib/node_cursor.dart

@@ -35,6 +35,8 @@ class NodeCursor {
   }
 
   nodeList() {
+    if (!isValid()) return [];  // or should we return null?
+
     var node = elements[index];
     var nodes = [];
 

test/compiler_spec.dart

@@ -29,6 +29,10 @@ main() {
       expect(element.text()).toEqual('angular');
     }));
 
+    it('should not throw on an empty list', inject((Compiler $compile) {
+      $compile([]);
+    }));
+
     it('should compile a directive in a child', inject((Compiler $compile) {
       var element = $('<div><div ng-bind="name"></div></div>');
       var template = $compile(element);