sync manager: write transaction exceptions

[strawberrybread]

#3937

Exception has been thrown: Can't commit a non-existing write transaction

specifically caused by triggerInsert() in syncManager when trying to insert

[Okuro3499]

@strawberrybread cleared most of the error except for this one which is work in progress

jni: ThrowingException 9, The Realm is already in a write transaction, .
Exception has been thrown: The Realm is already in a write transaction
Error during insertion into courses: The Realm is already in a write transaction
Transaction canceled for courses: The Realm is already in a write transaction
Error inserting into courses: The Realm is already in a write transaction