Update and fix manifest test

lib/docs/core/manifest.rb

@@ -27,7 +27,7 @@ module Docs
         aliases = eval data.split("ALIASES = ").last.split(";").first
 
         # set alias value
-        json["alias"] = aliases[json["slug"].to_sym]
+        json["alias"] = aliases[json["slug"].try(:to_sym)]
 
         result << json
       end

test/files/docs.json

@@ -1 +1 @@
-[{"name":"CSS","slug":"css","type":"mdn","release":null,"mtime":1420139788,"db_size":3460507},{"name":"DOM","slug":"dom","type":"mdn","release":null,"mtime":1420139789,"db_size":11399128},{"name":"DOM Events","slug":"dom_events","type":"mdn","release":null,"mtime":1420139790,"db_size":889020},{"name":"HTML","slug":"html~5","type":"mdn","version":"5","mtime":1420139791,"db_size":1835647},{"name":"HTML","slug":"html~4","type":"mdn","version":"4","mtime":1420139790,"db_size":1835646},{"name":"HTTP","slug":"http","type":"rfc","release":null,"mtime":1420139790,"db_size":183083},{"name":"JavaScript","slug":"javascript","type":"mdn","release":null,"mtime":1420139791,"db_size":4125477}]
+[{"name":"CSS","slug":"css","type":"mdn","release":null,"mtime":1420139788,"db_size":3460507,"alias":null},{"name":"DOM","slug":"dom","type":"mdn","release":null,"mtime":1420139789,"db_size":11399128,"alias":null},{"name":"DOM Events","slug":"dom_events","type":"mdn","release":null,"mtime":1420139790,"db_size":889020,"alias":null},{"name":"HTML","slug":"html~5","type":"mdn","version":"5","mtime":1420139791,"db_size":1835647,"alias":null},{"name":"HTML","slug":"html~4","type":"mdn","version":"4","mtime":1420139790,"db_size":1835646,"alias":null},{"name":"HTTP","slug":"http","type":"rfc","release":null,"mtime":1420139790,"db_size":183083,"alias":null},{"name":"JavaScript","slug":"javascript","type":"mdn","release":null,"mtime":1420139791,"db_size":4125477,"alias":"js"}]

test/lib/docs/core/manifest_test.rb

@@ -64,7 +64,7 @@ class ManifestTest < Minitest::Spec
       it "includes the doc's meta representation" do
         json = manifest.as_json
         assert_equal 1, json.length
-        assert_equal "{\"name\"=>\"Test\", \"db_size\"=>776533, :attribution=>\"foo\"}", json[0].to_s
+        assert_equal "{\"name\"=>\"Test\", \"db_size\"=>776533, :attribution=>\"foo\", \"alias\"=>nil}", json[0].to_s
       end
     end