Buffer is empty when created with no url.

spec/atom/buffer-spec.coffee

@@ -7,3 +7,7 @@ describe 'Buffer', ->
       filePath = require.resolve 'fixtures/sample.txt'
       buffer = new Buffer filePath
       expect(buffer.getText()).toBe fs.read(filePath)
+
+    it "loads an empty buffer if no url is given", ->
+      buffer = new Buffer null
+      expect(buffer.getText()).toBe ""

src/atom/buffer.coffee

@@ -7,7 +7,8 @@ class Buffer
   url: null
 
   constructor: (@url) ->
-    @aceDocument = new Document fs.read(@url)
+    text = if @url then fs.read(@url) else ""
+    @aceDocument = new Document text
 
   getText: ->
     @aceDocument.getValue()