tenderlove/nokogiri — pull request #605 by waj (2012-01-30 18:31:48+00:00)
Title: Fix segfault when invoking custom XPath function without arguments

Currently this produces a segmentation fault:

```ruby
x = Nokogiri::XML('')
ctx = Class.new {
def foo(x)
"FOO"
end
}.new

x.xpath('foo(x)', ctx)
```

The problem seems to be in ```ruby_funcall``` function that tries to initalize the arguments without checking.