fix(scope): allow sending emit/broadcast when no on()

Author: mhevery

lib/core/scope.dart

@@ -409,7 +409,8 @@ class _Streams {
     ScopeEvent event = new ScopeEvent(name, scope, data);
     Scope scopeCursor = scope;
     while(scopeCursor != null) {
-      if (scopeCursor._streams._scope == scopeCursor) {
+      if (scopeCursor._streams !=null &&
+          scopeCursor._streams._scope == scopeCursor) {
         ScopeStream stream = scopeCursor._streams._streams[name];
         if (stream != null) {
           event._currentScope = scopeCursor;

test/core/scope_spec.dart

@@ -216,6 +216,12 @@ main() => describe('scope', () {
   describe(r'events', () {
 
     describe('on', () {
+      it('should allow emit/broadcast when no listeners', inject((RootScope scope) {
+        scope.emit('foo');
+        scope.broadcast('foo');
+      }));
+
+
       it(r'should add listener for both emit and broadcast events', inject((RootScope rootScope) {
         var log = '',
         child = rootScope.createChild();