helper: Fix memory leak
Reported by ASAN:
Direct leak of 24 byte(s) in 6 object(s) allocated from:
#0 0x52dc10 in operator new(unsigned long) (/home/kfunk/devel/install/kf5-stable/bin/kdevelop+0x52dc10) #1 0x7f5fc09ab3d2 in Php::parameterType(Php::ParameterAst const*, KDevelop::TypePtr<KDevelop::AbstractType>, Php::EditorIntegrator*, KDevelop::DUContext*) /home/kfunk/devel/src/kf5/kdev-php-stable/duchain/helper.cpp:574:46 #2 0x7f5fc08e7aa7 in Php::TypeBuilder::visitParameter(Php::ParameterAst*) /home/kfunk/devel/src/kf5/kdev-php-stable/duchain/builders/typebuilder.cpp:389:30 ...