LibJS: Don't crash when calling byte_length for a detached ArrayBuffer

Author: https://github.com/PrestonLTaylor
Commit: 286bf307d2
Pull-request: https://github.com/SerenityOS/serenity/pull/19718
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibJS/Runtime/ArrayBuffer.h

@@ -32,7 +32,13 @@ public:
 
     virtual ~ArrayBuffer() override = default;
 
-    size_t byte_length() const { return buffer_impl().size(); }
+    size_t byte_length() const
+    {
+        if (is_detached())
+            return 0;
+
+        return buffer_impl().size();
+    }
 
     // [[ArrayBufferData]]
     ByteBuffer& buffer() { return buffer_impl(); }