Fix "Undefined variable $c" in Zend_XmlRpc_Server::setResponseClass()

[lapiudevgit]

The setResponseClass() method of Zend_XmlRpc_Server cannot be used because it throws an error: "Undefined variable $c".

This can be tested by running the corresponding unit test:

$ ./bin/phpunit --stderr -d memory_limit=-1  tests/Zend/XmlRpc/ServerTest.php
PHPUnit 9.6.21 by Sebastian Bergmann and contributors.
..........E........................E.                             37 / 37 (100%)
Time: 00:00.052, Memory: 8.00 MB
There were 2 errors:
1) Zend_XmlRpc_ServerTest::testSetResponseClass
Undefined variable $c
/var/www/html/limesurvey/upload/zf1-future/library/Zend/XmlRpc/Server.php:468
/var/www/html/limesurvey/upload/zf1-future/tests/Zend/XmlRpc/ServerTest.php:272
2) Zend_XmlRpc_ServerTest::testPassingInvalidResponseClassThrowsException
Undefined variable $c
/var/www/html/limesurvey/upload/zf1-future/library/Zend/XmlRpc/Server.php:468
/var/www/html/limesurvey/upload/zf1-future/tests/Zend/XmlRpc/ServerTest.php:667
ERRORS!
Tests: 37, Assertions: 98, Errors: 2.

Commit 273916d broke this by replacing the and operator by &&, because && has precedence over the assignment, while and doesn't. Adding the parenthesis solves the issue.

[gabrieljenik]

Thanks for merging. Do you expect this merge to be included in a release soon? I mention that as we need that in order to consume the repo through composer.

[develart-projects]

@gabrieljenik in coming days, hopefully. Now I'm trying to understand one last PR, before merge. Once that's done, we are free to go forward.

[gabrieljenik]

Thanks