void register(@NotNull Throwable e) {
      if (myException == null) {
        myException = e;
      }
      else {
        myException.addSuppressed(e);
      }

      if (!(e instanceof ProcessCanceledException)) {
        LOG.error(e);
      }
      else if (myAssertThreading) {
        LOG.error("ProcessCanceledException must not be thrown from document listeners for real document", new Throwable(e));
      }
    }
void register(@NotNull Throwable e)