AssertionError in getAtomicVar

[jrumbinas]

Calling DB.getAtomicVar() for non existing record will result in exception error (in 1.0.7)

Exception

java.lang.AssertionError
    at org.mapdb.StoreWAL.put(StoreWAL.java:199)
    at org.mapdb.Caches$HashTable.put(Caches.java:216)
    at org.mapdb.EngineWrapper.put(EngineWrapper.java:53)
    at org.mapdb.DB.createAtomicVar(DB.java:1393)
    at org.mapdb.DB.getAtomicVar(DB.java:1418)

Cause

    synchronized public <E> Atomic.Var<E> getAtomicVar(String name){
        ...
        if(type==null){
            ...
            return createAtomicVar(name, null, getDefaultSerializer());
        }
        return ret;
    }

[jankotek]

Store does not allow null values, which is initial value for Atomic.Var. I changed default value to empty string "". This is not issue in 2.0, since store handles null values.