Bug 196257 NPE when call ArgumentInfoList.argumentsIterator()
When call ArgumentInfoList.argumentsIterator(), it will throw NPE sometimes. This is caused the inner "arguments" member may not initialized when call this method.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/scripts/ArgumentInfoList.java
* Returns the argument definition given the name.
	 * 
	 * @param argumentName
	 *            name of the argument to get
	 * @return the argument definition with the specified name.
	 */
	public IArgumentInfo getArgument( String argumentName )
	{
		if ( arguments == null )
			return null;
		for ( Iterator iter = ( (ArrayList) arguments ).iterator( ); iter
				.hasNext( ); )
		{
			IArgumentInfo argument = (ArgumentInfo) iter.next( );
			if ( argument.getName( ).equalsIgnoreCase( argumentName ) )
				return argument;
		}
		return null;
	}
	/**
	 * Returns the iterator of argument definition. Each one is a list that
	 * contains <code>IArgumentInfo</code>.
	 * 
	 * @return iterator of argument definition.
	 */
	public Iterator argumentsIterator( )
	{
		return arguments.iterator( );
	}
}