fix: if there's no public/ directory, do not merge it in build

Author: hansl

lib/broccoli/angular2-app.js

@@ -87,18 +87,22 @@ Angular2App.prototype.toTree = function () {
     destDir: 'vendor'
   });
 
-  var publicDirTree = new Funnel('public', {
-    allowEmpty: true
-  });
-
-  var merged = mergeTrees([
+  var allTrees = [
     assetTree,
     tsTree,
     jsTree,
-    publicDirTree,
     this.index(),
     vendorNpmTree
-  ], { overwrite: true });
+  ];
+
+  if (fs.existsSync('public')) {
+    allTrees.push(new Funnel('public', {
+      exclude: ['**/.*'],  // Remove dot files.
+      allowEmpty: true
+    }));
+  }
+
+  var merged = mergeTrees(allTrees, { overwrite: true });
 
   return mergeTrees([merged, new SwManifest([merged])]);
 };