Don't send Link header when don't know prev and next links (#4633)

app/controllers/api/base_controller.rb

@@ -43,7 +43,7 @@ class Api::BaseController < ApplicationController
     links = []
     links << [next_path, [%w(rel next)]] if next_path
     links << [prev_path, [%w(rel prev)]] if prev_path
-    response.headers['Link'] = LinkHeader.new(links)
+    response.headers['Link'] = LinkHeader.new(links) unless links.empty?
   end
 
   def limit_param(default_limit)

spec/controllers/api/v1/favourites_controller_spec.rb

@@ -70,8 +70,7 @@ RSpec.describe Api::V1::FavouritesController, type: :controller do
         it 'does not add pagination headers if not necessary' do
           get :index
 
-          expect(response.headers['Link'].find_link(['rel', 'next'])).to eq nil
+          expect(response.headers['Link']).to eq nil
-          expect(response.headers['Link'].find_link(['rel', 'prev'])).to eq nil
         end
       end
     end