Return only present flows from Flows#to_ary

lib/rackstash/flows.rb

@@ -46,7 +46,7 @@ module Rackstash
     alias size length
 
     def to_ary
-      @flows.to_a
+      @flows.to_a.compact
     end
     alias to_a to_ary
 

spec/rackstash/flows_spec.rb

@@ -90,7 +90,7 @@ describe Rackstash::Flows do
     it 'adds nil flows if necessary' do
       flow = a_flow
       flows[3] = flow
-      expect(flows.to_a).to eql [nil, nil, nil, flow]
+      expect(flows.length).to eql 4
     end
 
     it 'tries to find a matching flow' do