Fix issue #330 - Crash with Friendica

import androidx.annotation.NonNull;

import androidx.preference.PreferenceManager;

import java.io.IOException;

import java.util.Random;

import java.util.concurrent.TimeUnit;

                            finalEcdh.saveServerKey(context, pushSubscription.server_key);

                        }

                    }

                } catch (IOException e) {

                } catch (Exception e) {

                    e.printStackTrace();

                }

            }