remove error handler not needed on PHP 8

Author: xabbuh

AbstractString.php

@@ -507,23 +507,14 @@ public function toByteString(string $toEncoding = null): ByteString
             return $b;
         }
 
-        set_error_handler(static fn ($t, $m) => throw new InvalidArgumentException($m));
-
         try {
-            try {
-                $b->string = mb_convert_encoding($this->string, $toEncoding, 'UTF-8');
-            } catch (InvalidArgumentException|\ValueError $e) {
-                if (!\function_exists('iconv')) {
-                    if ($e instanceof \ValueError) {
-                        throw new InvalidArgumentException($e->getMessage(), $e->getCode(), $e);
-                    }
-                    throw $e;
-                }
-
-                $b->string = iconv('UTF-8', $toEncoding, $this->string);
+            $b->string = mb_convert_encoding($this->string, $toEncoding, 'UTF-8');
+        } catch (\ValueError $e) {
+            if (!\function_exists('iconv')) {
+                throw new InvalidArgumentException($e->getMessage(), $e->getCode(), $e);
             }
-        } finally {
-            restore_error_handler();
+
+            $b->string = iconv('UTF-8', $toEncoding, $this->string);
         }
 
         return $b;