phpstan fixes

Author: cradu

src/Descriptor/Boot.php

@@ -37,6 +37,6 @@ public function init(IsoFile $isoFile, int &$offset): void
         $this->bootCatalogLocation = Buffer::readLSB($this->bytes, 4, $offset);
 
         // free some space...
-        unset($this->bytes);
+        $this->bytes = null;
     }
 }

src/Descriptor/Partition.php

@@ -50,7 +50,7 @@ public function init(IsoFile $isoFile, int &$offset): void
         $this->volPartitionSize = Buffer::readMSB($this->bytes, 8, $offset);
 
         // free some space...
-        unset($this->bytes);
+        $this->bytes = null;
         unset($unused);
     }
 }

src/Descriptor/Terminator.php

@@ -15,6 +15,6 @@ class Terminator extends Descriptor
     public function init(IsoFile $isoFile, int &$offset): void
     {
         // free some space...
-        unset($this->bytes);
+        $this->bytes = null;
     }
 }

src/Descriptor/UdfDescriptor.php

@@ -14,6 +14,6 @@ public function init(IsoFile $isoFile, int &$offset): void
         // TODO - add UDF processing
 
         // free some space...
-        unset($this->bytes);
+        $this->bytes = null;
     }
 }

src/Descriptor/Volume.php

@@ -116,7 +116,7 @@ public function init(IsoFile $isoFile, int &$offset): void
         $offset++;
 
         // free some space...
-        unset($this->bytes);
+        $this->bytes = null;
         unset($unused);
     }