Fix the Upload model being tainted after migration spec

spec/migrations/remove_empty_fork_networks_spec.rb

@@ -3,12 +3,19 @@ require Rails.root.join('db', 'post_migrate', '20171114104051_remove_empty_fork_
 describe RemoveEmptyForkNetworks, :migration do
   let!(:fork_networks) { table(:fork_networks) }
-  let(:deleted_project) { create(:project) }
-  let!(:empty_network) { create(:fork_network, id: 1, root_project_id: deleted_project.id) }
-  let!(:other_network) { create(:fork_network, id: 2, root_project_id: create(:project).id) }
+  let!(:projects) { table(:projects) }
+  let!(:fork_network_members) { table(:fork_network_members) }
+  let(:deleted_project) { projects.create! }
+  let!(:empty_network) { fork_networks.create!(id: 1, root_project_id: deleted_project.id) }
+  let!(:other_network) { fork_networks.create!(id: 2, root_project_id: projects.create.id) }
   before do
+    fork_network_members.create(fork_network_id: empty_network.id,
+                                project_id: empty_network.root_project_id)
+    fork_network_members.create(fork_network_id: other_network.id,
+                                project_id: other_network.root_project_id)
+
     deleted_project.destroy!
   end