message: [Reproducers] Fix unitialized pointer
  The FileCollector pointer in the FileSystem class wasn't initialized to
  nullptr during replay.
diff: @@ -39,7 +39,7 @@ public:
  m_mapped(false) {}
  FileSystem(llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> fs,
  bool mapped = false)
  - : m_fs(fs), m_mapped(mapped) {}
  + : m_fs(fs), m_collector(nullptr), m_mapped(mapped) {}
  FileSystem(const FileSystem &fs) = delete;
  FileSystem &operator=(const FileSystem &fs) = delete;
  