#74 small error in databindingexpression.inc.php

[Michael van Dam]

While trying to see if I could use 'dot paths' with
compiler properties, I think I've spotted a small error
in databindingexpression.inc.php.

In DataBindingExpression::generatePreStatement(), I think

$this->property->generatePreStatement($code);

should be replaced by

return $this->property->generatePreStatement($code);

Same problem in
DataBindingExpression::generateExpression() and
generatePostStatement() (though the latter doesn't
matter as it is now).