Merge pull request #1443 from poanetwork/ac-fix-migration-constructor-arguments

Fix constructor arguments migration

apps/explorer/priv/repo/migrations/20190215105501_add_constructor_arguments_to_smart_contracts.exs

@@ -2,6 +2,8 @@ defmodule Explorer.Repo.Migrations.AddConstructorArgumentsToSmartContracts do
   use Ecto.Migration
 
   def change do
+    execute("ALTER TABLE smart_contracts DROP COLUMN IF EXISTS constructor_arguments")
+
     alter table(:smart_contracts) do
       add(:constructor_arguments, :string, null: true)
     end