From a4633725d2c459015b2a1796e991ff04b01b749d Mon Sep 17 00:00:00 2001
From: Bryan Traywick <42215+bryantraywick@users.noreply.github.com>
Date: Fri, 4 Aug 2023 12:36:11 -0400
Subject: [PATCH] Fix NoMethodError when request Content-Type is blank.

---
 actionpack/lib/action_dispatch/http/mime_type.rb | 2 +-
 actionpack/test/controller/test_case_test.rb     | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/actionpack/lib/action_dispatch/http/mime_type.rb b/actionpack/lib/action_dispatch/http/mime_type.rb
index 6ef576e19d024..a8c2fe9b85430 100644
--- a/actionpack/lib/action_dispatch/http/mime_type.rb
+++ b/actionpack/lib/action_dispatch/http/mime_type.rb
@@ -163,7 +163,7 @@ def register_callback(&block)
 
       def lookup(string)
         # fallback to the media-type without parameters if it was not found
-        LOOKUP[string] || LOOKUP[string.split(";", 2)[0].rstrip] || Type.new(string)
+        LOOKUP[string] || LOOKUP[string.split(";", 2)[0]&.rstrip] || Type.new(string)
       end
 
       def lookup_by_extension(extension)
diff --git a/actionpack/test/controller/test_case_test.rb b/actionpack/test/controller/test_case_test.rb
index d82694bf0acc1..1deb3889cd7ce 100644
--- a/actionpack/test/controller/test_case_test.rb
+++ b/actionpack/test/controller/test_case_test.rb
@@ -607,6 +607,13 @@ def test_params_passing_doesnt_modify_in_place
     assert_equal "application/json", parsed_env["CONTENT_TYPE"]
   end
 
+  test "blank Content-Type header" do
+    @request.headers["Content-Type"] = ""
+    assert_raises(ActionDispatch::Http::MimeNegotiation::InvalidType) do
+      get :test_headers
+    end
+  end
+
   def test_using_as_json_sets_request_content_type_to_json
     post :render_body, params: { bool_value: true, str_value: "string", num_value: 2 }, as: :json