Do not raise exception when content_type is a empty string

When content type header is blank we were raising an exception because
`empty?` was being called on nil.

2 files changed, 6 insertions, 1 deletions

diff --git a/actionpack/lib/action_dispatch/http/response.rb b/actionpack/lib/action_dispatch/http/response.rb
index 357ca56036..f71c6afd6c 100644
--- a/actionpack/lib/action_dispatch/http/response.rb
+++ b/actionpack/lib/action_dispatch/http/response.rb
@@ -408,7 +408,7 @@ module ActionDispatch # :nodoc:
     def parse_content_type(content_type)
       if content_type
         type, charset = content_type.split(/;\s*charset=/)
-        type = nil if type.empty?
+        type = nil if type && type.empty?
         ContentTypeHeader.new(type, charset)
       else
         NullContentTypeHeader
diff --git a/actionpack/test/dispatch/response_test.rb b/actionpack/test/dispatch/response_test.rb
index 400af42bac..2df70704a1 100644
--- a/actionpack/test/dispatch/response_test.rb
+++ b/actionpack/test/dispatch/response_test.rb
@@ -110,6 +110,11 @@ class ResponseTest < ActiveSupport::TestCase
     assert_equal "application/aaron", @response.content_type
   end
 
+  def test_empty_content_type_returns_nil
+    @response.headers['Content-Type'] = ""
+    assert_equal nil, @response.content_type
+  end
+
   test "simple output" do
     @response.body = "Hello, World!"