Minor updates

ChronoPhage_GUI/app/src/main/java/de/hdm/dp/bd/chronophage/model/Task.java

@@ -66,10 +66,12 @@ public class Task {
    }
 
    public void end() {
-      Record r = this.getRecords().get(this.getRecords().size() - 1);
-      r.end();
-      this.active = false;
-      dbCalls.writeRecordForTask(r, this.id);
+      if (this.getRecords().size() > 0) {
+         Record r = this.getRecords().get(this.getRecords().size() - 1);
+         r.end();
+         this.active = false;
+         dbCalls.writeRecordForTask(r, this.id);
+      }
    }
 
    public List<Record> getRecords() {