#2 Handle null response from Perl script

[fyneman]

In PerlEngineImpl.java eval method, if the Perl script never talks back, the header will be null.

Suggest adding the following code:

if (header == null) { // If the Perl script never talks back,
return null; // the header will be null
}

as in

while (true) {
String header = input.readLine();

if (header == null) { // If the Perl script never talks back, header will be null
return null; // the header will be null
}

if (header.equals("BEGIN-RESPONSE")) {
...