Fix file_get_content exception when installing symfony 4.3-dev

Author: jlslew

src/Configurator/AbstractConfigurator.php

@@ -75,6 +75,10 @@ protected function markXmlData(Recipe $recipe, string $data): string
      */
     protected function updateData(string $file, string $data): bool
     {
+        if (!file_exists($file)) {
+            return false;
+        }
+
         $pieces = explode("\n", trim($data));
         $startMark = trim(reset($pieces));
         $endMark = trim(end($pieces));