Fixed dependency check for fpdfWriter

src/Writer/FpdfWriter.php

@@ -25,16 +25,17 @@ class FpdfWriter extends AbstractWriter
     public const WRITER_OPTION_MEASURE_UNIT = 'fpdf_measure_unit';
 
     public function __construct()
+    {
+    }
+
+    public function writeString(QrCodeInterface $qrCode): string
     {
         if(!\class_exists(\FPDF::class)){
             throw new \BadMethodCallException(
                 'The Fpdf writer requires FPDF as dependency but the class "\\FPDF" couldn\'t be found.'
             );
         }
-    }
-
-    public function writeString(QrCodeInterface $qrCode): string
-    {
+
         if ($qrCode->getValidateResult()) {
             throw new ValidationException(
                 'Built-in validation reader can not check fpdf qr codes: please disable via setValidateResult(false)'