Update ListContainer.java

I got an exception, when i used an empty hashset. Your method want to cast the empty hashset to a list(its impossible for sure :)) (java.lang.ClassCastException).

i solved the problem.

 public final void setCollection(Collection<T> backingList1){
...
}
Update ListContainer.java
Merge pull request #15 from waltR/patch-1

Update ListContainer.java