saml: Fix NULL return from saml_IdP_SAML2::getAssociationConfig().
saml: Fix NULL return from saml_IdP_SAML2::getAssociationConfig().

This function should not return NULL, but did so due to a missing
return statement. This patch adds that return statement, and fixes
the documentation for the function.
tectronics/simplesamlphp,tectronics/simplesamlphp,vivekrajenderan/simplesamlphp,vivekrajenderan/simplesamlphp,tectronics/simplesamlphp,tectronics/simplesamlphp,vivekrajenderan/simplesamlphp,vivekrajenderan/simplesamlphp,vivekrajenderan/simplesamlphp,tectronics/simplesamlphp