Handle case of no jobs to push_bulk, fixes #2997

lib/sidekiq/client.rb

@@ -84,6 +84,7 @@ module Sidekiq
     # than the number given if the middleware stopped processing for one or more jobs.
     def push_bulk(items)
       arg = items['args'].first
+      return [] unless arg # no jobs to push
       raise ArgumentError, "Bulk arguments must be an Array of Arrays: [[1], [2]]" if !arg.is_a?(Array)
 
       normed = normalize_item(items)

test/test_client.rb

@@ -126,6 +126,10 @@ class TestClient < Sidekiq::Test
         assert_match(/[0-9a-f]{12}/, jid)
       end
     end
+    it 'handles no jobs' do
+      result = Sidekiq::Client.push_bulk('class' => 'QueuedWorker', 'args' => [])
+      assert_equal 0, result.size
+    end
   end
 
   class BaseWorker