fix bootstrap error

Author: ZAYEC77

composer.json

@@ -4,7 +4,7 @@
     "license": "MIT",
     "minimum-stability": "dev",
     "require": {
-        "php": ">=5.4.0",
+        "php": ">=5.5.0||>=7.0",
         "yiisoft/yii2": ">=2.0.6",
         "symfony/filesystem": "^3.1",
         "symfony/finder": "^3.1",

src/Bootstrap.php

@@ -36,9 +36,11 @@ public function bootstrap($app)
             $app->controllerMap['env'] = [
                 'class' => 'nullref\core\console\EnvController',
             ];
-            $app->getModule('core')->controllerMap['migrate'] = [
-                'class' => 'nullref\core\console\MigrateController',
-            ];
+            if ($module = $app->getModule('core')) {
+                $module->controllerMap['migrate'] = [
+                    'class' => 'nullref\core\console\MigrateController',
+                ];
+            }
         }
         if (YII_ENV_DEV && class_exists('yii\gii\Module')) {
             Event::on(Gii::class, Gii::EVENT_BEFORE_ACTION, function (Event $event) {