fix: explicit nil to #compile for Rails 7.1

Author: Amnesthesia

lib/activerecord-import/import.rb

@@ -85,7 +85,7 @@ def valid_model?(model)
 
         model.run_callbacks(:validation) do
           if defined?(ActiveSupport::Callbacks::Filters::Environment) # ActiveRecord >= 4.1
-            runner = @validate_callbacks.compile
+            runner = @validate_callbacks.compile(nil)
             env = ActiveSupport::Callbacks::Filters::Environment.new(model, false, nil)
             if runner.respond_to?(:call) # ActiveRecord < 5.1
               runner.call(env)
@@ -105,7 +105,7 @@ def valid_model?(model)
               runner.invoke_after(env)
             end
           elsif @validate_callbacks.method(:compile).arity == 0 # ActiveRecord = 4.0
-            model.instance_eval @validate_callbacks.compile
+            model.instance_eval @validate_callbacks.compile(nil)
           else # ActiveRecord 3.x
             model.instance_eval @validate_callbacks.compile(nil, model)
           end