update test to check for nil instead of empty starting

before we were setting title as en empty string, but we think it's safer
to set it as nil (inside the parser)

if title is nil (or an empty string) it will be set as the url inside
Media.as_json

test/models/parser/facebook_profile_test.rb

@@ -153,7 +153,7 @@ def throwaway_url
 
     assert_equal Lapis::ErrorCodes::const_get('LOGIN_REQUIRED'), data[:error][:code]
     assert_match /Login required/, data[:error][:message]
-    assert data['title'].empty?
+    assert data['title'].nil?
     assert data['description'].empty?
   end
 
@@ -162,7 +162,7 @@ def throwaway_url
 
     assert_equal Lapis::ErrorCodes::const_get('LOGIN_REQUIRED'), data[:error][:code]
     assert_match /Login required/, data[:error][:message]
-    assert data['title'].empty?
+    assert data['title'].nil?
     assert data['description'].empty?
   end