getValue is causing a NPE on numOfKids = _numOfKids.removeFirst(); because _numOfKids is null.

public Object getValue(ELContext ctx, Object base, Object property)
			throws NullPointerException, PropertyNotFoundException, ELException {
		if (ctx == null) {
			throw new NullPointerException();
		}
		Integer numOfKids;
		Path path;
		if (base == null) { //init
			numOfKids = (Integer) ctx.getContext(AstIdentifier.class); //Number of siblings of AstIdentifier
			path = new Path();
		} else {
			*numOfKids = _numOfKids.removeFirst();*
			path = _paths.removeFirst();
		}

I have a zul page that calls a custom function defined in a tld file.

<listcell sclass="h20" label="@load(c:getMatchCompetitors(ma).date)"></listcell>

If i see the stack trace, the return value is correct. and also the properties are correct (i have a date property)
The NPE is caused whe trying to remove an element from an empty list. A test on empty should be executed before removing it
A similar test is present in getType method