Fixed rare crash

app/src/main/java/eu/faircode/email/ServiceSynchronize.java

@@ -65,6 +65,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import java.util.concurrent.ExecutorService;
+import java.util.concurrent.RejectedExecutionException;
 
 import javax.mail.AuthenticationFailedException;
 import javax.mail.Folder;
@@ -1185,6 +1186,7 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
                                                             " operations=" + partitions.get(key).size());
                                                 }
 
+                                                try {
                                                     executor.submit(new Helper.PriorityRunnable(key.getPriority()) {
                                                         @Override
                                                         public void run() {
@@ -1262,6 +1264,10 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
                                                             }
                                                         }
                                                     });
+                                                } catch (RejectedExecutionException ex) {
+                                                    Log.w(ex);
+                                                    break;
+                                                }
                                             }
                                         }
                                     }