x-Axis value of 0 (Zero) not displayed

That's really a nice script.
Very easy to use and helpful to visualize data.

Unfortunately data linked to a x-axis value of 0 (zero) is not displayed.
After a litte debugging I found the solution:

In line 262 the empty-function is used. For this function 0 is equal empty.

To solve the issue just replace empty($value) by _empty($value) and create a new funtion

function _empty($string){
$string = trim($string);
if(!is_numeric($string)) return empty($string);
return FALSE;
}

somewhere in the class.

Now you will see the x-axis value.