bugfix: wrapped the building of authsource config with issets. (#539)

* Adjusted the silent fail to log a warning when $this->getLdap() fails

the silent fail on searchformultiple(...) did not show anything in the log when actually it was the $this->getLdap() that failed.

* Bugfix: Wrapped the building of authsource config with issets

Not doing this gave me errors about ldap.port and ldap.timeout not being an integer (but NULL) from Configuration.php

Dec 23 08:28:10 simplesamlphp WARNING [94b0f44d76] AttributeAddFromLDAP: exception = exception 'Exception' with message 'ldap:AuthProcess: The option 'ldap.port' is not a valid integer value.' in /Users/remy/git/saml-IdP/lib/SimpleSAML/Configuration.php:737
Stack trace:
#0 /Users/remy/git/saml-IdP/modules/ldap/lib/Auth/Process/BaseFilter.php(267): SimpleSAML_Configuration->getInteger('ldap.port', 389)
#1 /Users/remy/git/saml-IdP/modules/ldap/lib/Auth/Process/AttributeAddFromLDAP.php(172): sspmod_ldap_Auth_Process_BaseFilter->getLdap()
...

* removed the @ as thijskh suggested...

* feature: AttributeCopy can take array for 1 attribute

* Revert "feature: AttributeCopy can take array for 1 attribute"

This reverts commit 78ccac061eab0fc4a0680e2aaf9ae07c3b6a29ac.

* BaseFilter.php: fix indent and added more isset checks...

* BaseFilter.php: removed an unneeded if ($authsource['search.enable'] ....

Since I moved this code into an if that already only gets executed when authsource['search.enable'] = true it is no longer needed in this check....