#fixed code
                              public Symbol getSymbolForInstancesOf(FunctionType fn) {
    Preconditions.checkState(fn.isConstructor() || fn.isInterface());
    ObjectType pType = fn.getPrototype();
    return getSymbolForName(fn.getSource(), pType.getReferenceName());
  }
#vulnerable code 
                              public Symbol getSymbolForInstancesOf(FunctionType fn) {
    Preconditions.checkState(fn.isConstructor() || fn.isInterface());
    ObjectType pType = fn.getPrototype();
    String name = pType.getReferenceName();
    if (name == null || globalScope == null) {
      return null;
    }

    Node source = fn.getSource();
    return (source == null ?
        globalScope : getEnclosingScope(source)).getSlot(name);
  } 
                            #location 11 
                            #vulnerability type NULL_DEREFERENCE