If JSON parsing fails on reading the active list, just set it to an empty hash

lib/vagrant/active_list.rb

@@ -26,7 +26,11 @@ module Vagrant
       @list ||= {}
       return @list unless File.file?(path)
       File.open(path, "r") do |f|
+        begin
           @list = JSON.parse(f.read)
+        rescue Exception
+          @list = {}
+        end
 
         # This forces earlier versions of Vagrant to use the new hash
         # format. Clearing out the old data isn't a big deal since it

test/vagrant/active_list_test.rb

@@ -57,6 +57,18 @@ class ActiveListTest < Test::Unit::TestCase
       assert result.equal?(@list.list)
       assert result.equal?(@list.list)
     end
+
+    should "be an empty hash if JSON parsing raises an exception" do
+      file = mock("file")
+      file.stubs(:read)
+      File.expects(:file?).returns(true)
+      File.expects(:open).with(@list.path, 'r').once.yields(file)
+      JSON.expects(:parse).raises(Exception)
+
+      assert_nothing_raised do
+        assert_equal Hash.new, @list.list(true)
+      end
+    end
   end
 
   context "filter list" do