Fix deprecation warnings for PHP 8.1

src/Drivers/Abstract/AbstractFont.php

@@ -56,7 +56,7 @@ abstract class AbstractFont implements FontInterface
 
     public function hasFilename(): bool
     {
-        return is_file($this->filename);
+        return !is_null($this->filename) && is_file($this->filename);
     }
 
     public function color($color): FontInterface

src/Drivers/Gd/Modifiers/DrawPolygonModifier.php

@@ -22,7 +22,6 @@ class DrawPolygonModifier extends AbstractDrawModifier implements ModifierInterf
                 imagefilledpolygon(
                     $frame->getCore(),
                     $this->polygon()->toArray(),
-                    $this->polygon()->count(),
                     $this->getBackgroundColor()->toInt()
                 );
             }

src/Drivers/Imagick/Image.php

@@ -77,14 +77,14 @@ class Image extends AbstractImage implements ImageInterface, Iterator
         return $this->imagick->getNumberImages();
     }
 
-    public function current()
+    public function current(): mixed
     {
         $this->imagick->setIteratorIndex($this->iteratorIndex);
 
         return new Frame($this->imagick->current());
     }
 
-    public function key()
+    public function key(): mixed
     {
         return $this->iteratorIndex;
     }