Debug IP address parameter

Added a debug IP Address to be used when working locally for example.
Also handled a PHP warning in case nothing was returned by getFreegeoip() function
You could do both. I however don't think it is necessary since it is not available to edit the value from the front end and only the backend can change the value.
In order to be bulletproof, htmlspecialchar would not really help. I'd use JFilterInput::clean instead to prevent not only html tags but also xss attacks.