fix(scope): skip scopes whithot event on broadcast

Author: mhevery

lib/core/scope.dart

@@ -513,15 +513,19 @@ class _Streams {
         scope = queue.removeFirst();
         scopeStreams = scope._streams;
         assert(scopeStreams._scope == scope);
-        assert(scopeStreams._streams.containsKey(name));
-        var stream = scopeStreams._streams[name];
-        event._currentScope = scope;
-        stream._fire(event);
+        if(scopeStreams._streams.containsKey(name)) {
+          var stream = scopeStreams._streams[name];
+          event._currentScope = scope;
+          stream._fire(event);
+        }
         // Reverse traversal so that when the queue is read it is correct order.
         var childScope = scope._childTail;
         while(childScope != null) {
           scopeStreams = childScope._streams;
-          if (scopeStreams != null) queue.addFirst(scopeStreams._scope);
+          if (scopeStreams != null &&
+              scopeStreams._typeCounts.containsKey(name)) {
+            queue.addFirst(scopeStreams._scope);
+          }
           childScope = childScope._prev;
         }
       }

test/core/scope_spec.dart

@@ -448,6 +448,19 @@ main() => describe('scope', () {
           expect(result.name).toBe('some');
           expect(result.targetScope).toBe(child1);
         }));
+
+
+        it('should skip scopes which dont have given event',
+            inject((RootScope rootScope, Logger log) {
+          var child1 = rootScope.createChild('A');
+          rootScope.createChild('A1');
+          rootScope.createChild('A2');
+          rootScope.createChild('A3');
+          var child2 = rootScope.createChild('B');
+          child2.on('event').listen((e) => log(e.data));
+          rootScope.broadcast('event', 'OK');
+          expect(log).toEqual(['OK']);
+        }));
       });