NPE when using functions

[MaximPixel]

There is an unhandled error in Xsoup when using XPath expressions with query in any functions. For example:
//tr[contains(td[1]/text(), 'something')]/td[2]/text()
This causes a NullPointerException at line 53 in CombiningEvaluator due to a null return value in the XPathParser::byFunction method.

[sutra]

The contains supports AttributeWithValueContaining only:

xsoup/src/main/java/us/codecraft/xsoup/xevaluator/XPathParser.java

Line 39 in bd24b1b

return new Evaluator.AttributeWithValueContaining(param[0], param[1]);