continues with other migrations if we can't delete the 'user_firsts' table

db/migrate/20160407160756_remove_user_firsts.rb

@@ -1,5 +1,8 @@
 class RemoveUserFirsts < ActiveRecord::Migration
   def up
     drop_table :user_firsts
+  rescue
+    # continues with other migrations if we can't delete that table
+    nil
   end
 end